StringStream and parseJson, parseCfg, parseSql et al for the vm (#10746)

15 files changed, 354 insertions, 403 deletions

diff --git a/compiler/ccgmerge.nim b/compiler/ccgmerge.nim
index ccb5a7635..56b17440e 100644
--- a/compiler/ccgmerge.nim
+++ b/compiler/ccgmerge.nim
@@ -145,38 +145,34 @@ proc atEndMark(buf: cstring, pos: int): bool =
 
 proc readVerbatimSection(L: var TBaseLexer): Rope =
   var pos = L.bufpos
-  var buf = L.buf
   var r = newStringOfCap(30_000)
   while true:
-    case buf[pos]
+    case L.buf[pos]
     of CR:
       pos = nimlexbase.handleCR(L, pos)
-      buf = L.buf
       r.add('\L')
     of LF:
       pos = nimlexbase.handleLF(L, pos)
-      buf = L.buf
       r.add('\L')
     of '\0':
       doAssert(false, "ccgmerge: expected: " & NimMergeEndMark)
       break
     else:
-      if atEndMark(buf, pos):
+      if atEndMark(L.buf, pos):
         inc pos, NimMergeEndMark.len
         break
-      r.add(buf[pos])
+      r.add(L.buf[pos])
       inc pos
   L.bufpos = pos
   result = r.rope
 
 proc readKey(L: var TBaseLexer, result: var string) =
   var pos = L.bufpos
-  var buf = L.buf
   setLen(result, 0)
-  while buf[pos] in IdentChars:
-    result.add(buf[pos])
+  while L.buf[pos] in IdentChars:
+    result.add(L.buf[pos])
     inc pos
-  if buf[pos] != ':': doAssert(false, "ccgmerge: ':' expected")
+  if L.buf[pos] != ':': doAssert(false, "ccgmerge: ':' expected")
   L.bufpos = pos + 1 # skip ':'
 
 proc newFakeType(id: int): PType =
diff --git a/compiler/lexer.nim b/compiler/lexer.nim
index 5eaa4c09f..0dd6245b0 100644
--- a/compiler/lexer.nim
+++ b/compiler/lexer.nim
@@ -318,17 +318,16 @@ template eatChar(L: var TLexer, t: var TToken) =
 proc getNumber(L: var TLexer, result: var TToken) =
   proc matchUnderscoreChars(L: var TLexer, tok: var TToken, chars: set[char]): Natural =
     var pos = L.bufpos              # use registers for pos, buf
-    var buf = L.buf
     result = 0
     while true:
-      if buf[pos] in chars:
-        add(tok.literal, buf[pos])
+      if L.buf[pos] in chars:
+        add(tok.literal, L.buf[pos])
         inc(pos)
         inc(result)
       else:
         break
-      if buf[pos] == '_':
-        if buf[pos+1] notin chars:
+      if L.buf[pos] == '_':
+        if L.buf[pos+1] notin chars:
           lexMessage(L, errGenerated,
             "only single underscores may occur in a token and token may not " &
             "end with an underscore: e.g. '1__1' and '1_' are invalid")
@@ -339,9 +338,8 @@ proc getNumber(L: var TLexer, result: var TToken) =
 
   proc matchChars(L: var TLexer, tok: var TToken, chars: set[char]) =
     var pos = L.bufpos              # use registers for pos, buf
-    var buf = L.buf
-    while buf[pos] in chars:
-      add(tok.literal, buf[pos])
+    while L.buf[pos] in chars:
+      add(tok.literal, L.buf[pos])
       inc(pos)
     L.bufpos = pos
 
@@ -800,25 +798,23 @@ type
 
 proc getString(L: var TLexer, tok: var TToken, mode: StringMode) =
   var pos = L.bufpos
-  var buf = L.buf                 # put `buf` in a register
   var line = L.lineNumber         # save linenumber for better error message
   tokenBegin(tok, pos - ord(mode == raw))
   inc pos # skip "
-  if buf[pos] == '\"' and buf[pos+1] == '\"':
+  if L.buf[pos] == '\"' and L.buf[pos+1] == '\"':
     tok.tokType = tkTripleStrLit # long string literal:
     inc(pos, 2)               # skip ""
     # skip leading newline:
-    if buf[pos] in {' ', '\t'}:
+    if L.buf[pos] in {' ', '\t'}:
       var newpos = pos+1
-      while buf[newpos] in {' ', '\t'}: inc newpos
-      if buf[newpos] in {CR, LF}: pos = newpos
+      while L.buf[newpos] in {' ', '\t'}: inc newpos
+      if L.buf[newpos] in {CR, LF}: pos = newpos
     pos = handleCRLF(L, pos)
-    buf = L.buf
     while true:
-      case buf[pos]
+      case L.buf[pos]
       of '\"':
-        if buf[pos+1] == '\"' and buf[pos+2] == '\"' and
-            buf[pos+3] != '\"':
+        if L.buf[pos+1] == '\"' and L.buf[pos+2] == '\"' and
+            L.buf[pos+3] != '\"':
           tokenEndIgnore(tok, pos+2)
           L.bufpos = pos + 3 # skip the three """
           break
@@ -827,7 +823,6 @@ proc getString(L: var TLexer, tok: var TToken, mode: StringMode) =
       of CR, LF:
         tokenEndIgnore(tok, pos)
         pos = handleCRLF(L, pos)
-        buf = L.buf
         add(tok.literal, "\n")
       of nimlexbase.EndOfFile:
         tokenEndIgnore(tok, pos)
@@ -838,16 +833,16 @@ proc getString(L: var TLexer, tok: var TToken, mode: StringMode) =
         L.bufpos = pos
         break
       else:
-        add(tok.literal, buf[pos])
+        add(tok.literal, L.buf[pos])
         inc(pos)
   else:
     # ordinary string literal
     if mode != normal: tok.tokType = tkRStrLit
     else: tok.tokType = tkStrLit
     while true:
-      var c = buf[pos]
+      var c = L.buf[pos]
       if c == '\"':
-        if mode != normal and buf[pos+1] == '\"':
+        if mode != normal and L.buf[pos+1] == '\"':
           inc(pos, 2)
           add(tok.literal, '"')
         else:
@@ -885,10 +880,9 @@ proc getCharacter(L: var TLexer, tok: var TToken) =
 proc getSymbol(L: var TLexer, tok: var TToken) =
   var h: Hash = 0
   var pos = L.bufpos
-  var buf = L.buf
   tokenBegin(tok, pos)
   while true:
-    var c = buf[pos]
+    var c = L.buf[pos]
     case c
     of 'a'..'z', '0'..'9', '\x80'..'\xFF':
       h = h !& ord(c)
@@ -898,7 +892,7 @@ proc getSymbol(L: var TLexer, tok: var TToken) =
       h = h !& ord(c)
       inc(pos)
     of '_':
-      if buf[pos+1] notin SymChars:
+      if L.buf[pos+1] notin SymChars:
         lexMessage(L, errGenerated, "invalid token: trailing underscore")
         break
       inc(pos)
@@ -923,11 +917,10 @@ proc endOperator(L: var TLexer, tok: var TToken, pos: int,
 
 proc getOperator(L: var TLexer, tok: var TToken) =
   var pos = L.bufpos
-  var buf = L.buf
   tokenBegin(tok, pos)
   var h: Hash = 0
   while true:
-    var c = buf[pos]
+    var c = L.buf[pos]
     if c notin OpChars: break
     h = h !& ord(c)
     inc(pos)
@@ -936,10 +929,10 @@ proc getOperator(L: var TLexer, tok: var TToken) =
   # advance pos but don't store it in L.bufpos so the next token (which might
   # be an operator too) gets the preceding spaces:
   tok.strongSpaceB = 0
-  while buf[pos] == ' ':
+  while L.buf[pos] == ' ':
     inc pos
     inc tok.strongSpaceB
-  if buf[pos] in {CR, LF, nimlexbase.EndOfFile}:
+  if L.buf[pos] in {CR, LF, nimlexbase.EndOfFile}:
     tok.strongSpaceB = -1
 
 proc getPrecedence*(tok: TToken, strongSpaces: bool): int =
@@ -980,9 +973,8 @@ proc getPrecedence*(tok: TToken, strongSpaces: bool): int =
 
 proc newlineFollows*(L: TLexer): bool =
   var pos = L.bufpos
-  var buf = L.buf
   while true:
-    case buf[pos]
+    case L.buf[pos]
     of ' ', '\t':
       inc(pos)
     of CR, LF:
@@ -990,49 +982,47 @@ proc newlineFollows*(L: TLexer): bool =
       break
     of '#':
       inc(pos)
-      if buf[pos] == '#': inc(pos)
-      if buf[pos] != '[': return true
+      if L.buf[pos] == '#': inc(pos)
+      if L.buf[pos] != '[': return true
     else:
       break
 
 proc skipMultiLineComment(L: var TLexer; tok: var TToken; start: int;
                           isDoc: bool) =
   var pos = start
-  var buf = L.buf
   var toStrip = 0
   tokenBegin(tok, pos)
   # detect the amount of indentation:
   if isDoc:
     toStrip = getColNumber(L, pos)
-    while buf[pos] == ' ': inc pos
-    if buf[pos] in {CR, LF}:
+    while L.buf[pos] == ' ': inc pos
+    if L.buf[pos] in {CR, LF}:
       pos = handleCRLF(L, pos)
-      buf = L.buf
       toStrip = 0
-      while buf[pos] == ' ':
+      while L.buf[pos] == ' ':
         inc pos
         inc toStrip
   var nesting = 0
   while true:
-    case buf[pos]
+    case L.buf[pos]
     of '#':
       if isDoc:
-        if buf[pos+1] == '#' and buf[pos+2] == '[':
+        if L.buf[pos+1] == '#' and L.buf[pos+2] == '[':
           inc nesting
         tok.literal.add '#'
-      elif buf[pos+1] == '[':
+      elif L.buf[pos+1] == '[':
         inc nesting
       inc pos
     of ']':
       if isDoc:
-        if buf[pos+1] == '#' and buf[pos+2] == '#':
+        if L.buf[pos+1] == '#' and L.buf[pos+2] == '#':
           if nesting == 0:
             tokenEndIgnore(tok, pos+2)
             inc(pos, 3)
             break
           dec nesting
         tok.literal.add ']'
-      elif buf[pos+1] == '#':
+      elif L.buf[pos+1] == '#':
         if nesting == 0:
           tokenEndIgnore(tok, pos+1)
           inc(pos, 2)
@@ -1042,14 +1032,13 @@ proc skipMultiLineComment(L: var TLexer; tok: var TToken; start: int;
     of CR, LF:
       tokenEndIgnore(tok, pos)
       pos = handleCRLF(L, pos)
-      buf = L.buf
       # strip leading whitespace:
       when defined(nimpretty): tok.literal.add "\L"
       if isDoc:
         when not defined(nimpretty): tok.literal.add "\n"
         inc tok.iNumber
         var c = toStrip
-        while buf[pos] == ' ' and c > 0:
+        while L.buf[pos] == ' ' and c > 0:
           inc pos
           dec c
     of nimlexbase.EndOfFile:
@@ -1057,7 +1046,7 @@ proc skipMultiLineComment(L: var TLexer; tok: var TToken; start: int;
       lexMessagePos(L, errGenerated, pos, "end of multiline comment expected")
       break
     else:
-      if isDoc or defined(nimpretty): tok.literal.add buf[pos]
+      if isDoc or defined(nimpretty): tok.literal.add L.buf[pos]
       inc(pos)
   L.bufpos = pos
   when defined(nimpretty):
@@ -1065,49 +1054,47 @@ proc skipMultiLineComment(L: var TLexer; tok: var TToken; start: int;
 
 proc scanComment(L: var TLexer, tok: var TToken) =
   var pos = L.bufpos
-  var buf = L.buf
   tok.tokType = tkComment
   # iNumber contains the number of '\n' in the token
   tok.iNumber = 0
-  assert buf[pos+1] == '#'
+  assert L.buf[pos+1] == '#'
   when defined(nimpretty):
     tok.commentOffsetA = L.offsetBase + pos - 1
 
-  if buf[pos+2] == '[':
+  if L.buf[pos+2] == '[':
     skipMultiLineComment(L, tok, pos+3, true)
     return
   tokenBegin(tok, pos)
   inc(pos, 2)
 
   var toStrip = 0
-  while buf[pos] == ' ':
+  while L.buf[pos] == ' ':
     inc pos
     inc toStrip
 
   while true:
     var lastBackslash = -1
-    while buf[pos] notin {CR, LF, nimlexbase.EndOfFile}:
-      if buf[pos] == '\\': lastBackslash = pos+1
-      add(tok.literal, buf[pos])
+    while L.buf[pos] notin {CR, LF, nimlexbase.EndOfFile}:
+      if L.buf[pos] == '\\': lastBackslash = pos+1
+      add(tok.literal, L.buf[pos])
       inc(pos)
     tokenEndIgnore(tok, pos)
     pos = handleCRLF(L, pos)
-    buf = L.buf
     var indent = 0
-    while buf[pos] == ' ':
+    while L.buf[pos] == ' ':
       inc(pos)
       inc(indent)
 
-    if buf[pos] == '#' and buf[pos+1] == '#':
+    if L.buf[pos] == '#' and L.buf[pos+1] == '#':
       tok.literal.add "\n"
       inc(pos, 2)
       var c = toStrip
-      while buf[pos] == ' ' and c > 0:
+      while L.buf[pos] == ' ' and c > 0:
         inc pos
         dec c
       inc tok.iNumber
     else:
-      if buf[pos] > ' ':
+      if L.buf[pos] > ' ':
         L.indentAhead = indent
       tokenEndIgnore(tok, pos)
       break
@@ -1117,7 +1104,6 @@ proc scanComment(L: var TLexer, tok: var TToken) =
 
 proc skip(L: var TLexer, tok: var TToken) =
   var pos = L.bufpos
-  var buf = L.buf
   tokenBegin(tok, pos)
   tok.strongSpaceA = 0
   when defined(nimpretty):
@@ -1127,7 +1113,7 @@ proc skip(L: var TLexer, tok: var TToken) =
     tok.commentOffsetB = tok.commentOffsetA
     tok.line = -1
   while true:
-    case buf[pos]
+    case L.buf[pos]
     of ' ':
       inc(pos)
       inc(tok.strongSpaceA)
@@ -1137,13 +1123,12 @@ proc skip(L: var TLexer, tok: var TToken) =
     of CR, LF:
       tokenEndPrevious(tok, pos)
       pos = handleCRLF(L, pos)
-      buf = L.buf
       var indent = 0
       while true:
-        if buf[pos] == ' ':
+        if L.buf[pos] == ' ':
           inc(pos)
           inc(indent)
-        elif buf[pos] == '#' and buf[pos+1] == '[':
+        elif L.buf[pos] == '#' and L.buf[pos+1] == '[':
           when defined(nimpretty):
             hasComment = true
             if tok.line < 0:
@@ -1151,32 +1136,30 @@ proc skip(L: var TLexer, tok: var TToken) =
               commentIndent = indent
           skipMultiLineComment(L, tok, pos+2, false)
           pos = L.bufpos
-          buf = L.buf
         else:
           break
       tok.strongSpaceA = 0
       when defined(nimpretty):
-        if buf[pos] == '#' and tok.line < 0: commentIndent = indent
-      if buf[pos] > ' ' and (buf[pos] != '#' or buf[pos+1] == '#'):
+        if L.buf[pos] == '#' and tok.line < 0: commentIndent = indent
+      if L.buf[pos] > ' ' and (L.buf[pos] != '#' or L.buf[pos+1] == '#'):
         tok.indent = indent
         L.currLineIndent = indent
         break
     of '#':
       # do not skip documentation comment:
-      if buf[pos+1] == '#': break
+      if L.buf[pos+1] == '#': break
       when defined(nimpretty):
         hasComment = true
         if tok.line < 0:
           tok.line = L.lineNumber
 
-      if buf[pos+1] == '[':
+      if L.buf[pos+1] == '[':
         skipMultiLineComment(L, tok, pos+2, false)
         pos = L.bufpos
-        buf = L.buf
       else:
         tokenBegin(tok, pos)
-        while buf[pos] notin {CR, LF, nimlexbase.EndOfFile}:
-          when defined(nimpretty): tok.literal.add buf[pos]
+        while L.buf[pos] notin {CR, LF, nimlexbase.EndOfFile}:
+          when defined(nimpretty): tok.literal.add L.buf[pos]
           inc(pos)
         tokenEndIgnore(tok, pos+1)
         when defined(nimpretty):
diff --git a/compiler/nimlexbase.nim b/compiler/nimlexbase.nim
index 2e7416645..214147a2b 100644
--- a/compiler/nimlexbase.nim
+++ b/compiler/nimlexbase.nim
@@ -39,8 +39,7 @@ const
 type
   TBaseLexer* = object of RootObj
     bufpos*: int
-    buf*: cstring
-    bufLen*: int              # length of buffer in characters
+    buf*: string
     stream*: PLLStream        # we read from this stream
     lineNumber*: int          # the current line number
                               # private data:
@@ -65,11 +64,7 @@ proc handleLF*(L: var TBaseLexer, pos: int): int
   # of the LF.
 # implementation
 
-const
-  chrSize = sizeof(char)
-
 proc closeBaseLexer(L: var TBaseLexer) =
-  dealloc(L.buf)
   llStreamClose(L.stream)
 
 proc fillBuffer(L: var TBaseLexer) =
@@ -80,14 +75,13 @@ proc fillBuffer(L: var TBaseLexer) =
     oldBufLen: int
   # we know here that pos == L.sentinel, but not if this proc
   # is called the first time by initBaseLexer()
-  assert(L.sentinel < L.bufLen)
-  toCopy = L.bufLen - L.sentinel - 1
+  assert(L.sentinel < L.buf.len)
+  toCopy = L.buf.len - L.sentinel - 1
   assert(toCopy >= 0)
   if toCopy > 0:
-    moveMem(L.buf, addr(L.buf[L.sentinel + 1]), toCopy * chrSize)
+    moveMem(addr L.buf[0], addr L.buf[L.sentinel + 1], toCopy)
     # "moveMem" handles overlapping regions
-  charsRead = llStreamRead(L.stream, addr(L.buf[toCopy]),
-                           (L.sentinel + 1) * chrSize) div chrSize
+  charsRead = llStreamRead(L.stream, addr L.buf[toCopy], L.sentinel + 1)
   s = toCopy + charsRead
   if charsRead < L.sentinel + 1:
     L.buf[s] = EndOfFile      # set end marker
@@ -96,7 +90,7 @@ proc fillBuffer(L: var TBaseLexer) =
     # compute sentinel:
     dec(s)                    # BUGFIX (valgrind)
     while true:
-      assert(s < L.bufLen)
+      assert(s < L.buf.len)
       while (s >= 0) and not (L.buf[s] in NewLines): dec(s)
       if s >= 0:
         # we found an appropriate character for a sentinel:
@@ -105,17 +99,16 @@ proc fillBuffer(L: var TBaseLexer) =
       else:
         # rather than to give up here because the line is too long,
         # double the buffer's size and try again:
-        oldBufLen = L.bufLen
-        L.bufLen = L.bufLen * 2
-        L.buf = cast[cstring](realloc(L.buf, L.bufLen * chrSize))
-        assert(L.bufLen - oldBufLen == oldBufLen)
+        oldBufLen = L.buf.len
+        L.buf.setLen(L.buf.len * 2)
+        assert(L.buf.len - oldBufLen == oldBufLen)
         charsRead = llStreamRead(L.stream, addr(L.buf[oldBufLen]),
-                                 oldBufLen * chrSize) div chrSize
+                                 oldBufLen)
         if charsRead < oldBufLen:
           L.buf[oldBufLen + charsRead] = EndOfFile
           L.sentinel = oldBufLen + charsRead
           break
-        s = L.bufLen - 1
+        s = L.buf.len - 1
 
 proc fillBaseLexer(L: var TBaseLexer, pos: int): int =
   assert(pos <= L.sentinel)
@@ -149,8 +142,7 @@ proc openBaseLexer(L: var TBaseLexer, inputstream: PLLStream, bufLen = 8192) =
   assert(bufLen > 0)
   L.bufpos = 0
   L.offsetBase = 0
-  L.bufLen = bufLen
-  L.buf = cast[cstring](alloc(bufLen * chrSize))
+  L.buf = newString(bufLen)
   L.sentinel = bufLen - 1
   L.lineStart = 0
   L.lineNumber = 1            # lines start at 1
diff --git a/compiler/vmgen.nim b/compiler/vmgen.nim
index ab2ac8707..092c25a46 100644
--- a/compiler/vmgen.nim
+++ b/compiler/vmgen.nim
@@ -2039,6 +2039,8 @@ proc gen(c: PCtx; n: PNode; dest: var TDest; flags: TGenFlags = {}) =
     genConv(c, n, n.sons[1], dest)
   of nkObjDownConv:
     genConv(c, n, n.sons[0], dest)
+  of nkObjUpConv:
+    genConv(c, n, n.sons[0], dest)
   of nkVarSection, nkLetSection:
     unused(c, n, dest)
     genVarSection(c, n)
diff --git a/lib/packages/docutils/rst.nim b/lib/packages/docutils/rst.nim
index 615119135..0b077b1f1 100644
--- a/lib/packages/docutils/rst.nim
+++ b/lib/packages/docutils/rst.nim
@@ -155,18 +155,17 @@ proc getAdornment(L: var Lexer, tok: var Token) =
 
 proc getIndentAux(L: var Lexer, start: int): int =
   var pos = start
-  var buf = L.buf
   # skip the newline (but include it in the token!)
-  if buf[pos] == '\x0D':
-    if buf[pos + 1] == '\x0A': inc(pos, 2)
+  if L.buf[pos] == '\x0D':
+    if L.buf[pos + 1] == '\x0A': inc(pos, 2)
     else: inc(pos)
-  elif buf[pos] == '\x0A':
+  elif L.buf[pos] == '\x0A':
     inc(pos)
   if L.skipPounds:
-    if buf[pos] == '#': inc(pos)
-    if buf[pos] == '#': inc(pos)
+    if L.buf[pos] == '#': inc(pos)
+    if L.buf[pos] == '#': inc(pos)
   while true:
-    case buf[pos]
+    case L.buf[pos]
     of ' ', '\x0B', '\x0C':
       inc(pos)
       inc(result)
@@ -175,9 +174,9 @@ proc getIndentAux(L: var Lexer, start: int): int =
       result = result - (result mod 8) + 8
     else:
       break                   # EndOfFile also leaves the loop
-  if buf[pos] == '\0':
+  if L.buf[pos] == '\0':
     result = 0
-  elif (buf[pos] == '\x0A') or (buf[pos] == '\x0D'):
+  elif (L.buf[pos] == '\x0A') or (L.buf[pos] == '\x0D'):
     # look at the next line for proper indentation:
     result = getIndentAux(L, pos)
   L.bufpos = pos              # no need to set back buf
diff --git a/lib/pure/lexbase.nim b/lib/pure/lexbase.nim
index e38acd5ef..11ec45a37 100644
--- a/lib/pure/lexbase.nim
+++ b/lib/pure/lexbase.nim
@@ -28,11 +28,7 @@ type
   BaseLexer* = object of RootObj ## the base lexer. Inherit your lexer from
                                  ## this object.
     bufpos*: int              ## the current position within the buffer
-    when defined(js):         ## the buffer itself
-      buf*: string
-    else:
-      buf*: cstring
-    bufLen*: int              ## length of buffer in characters
+    buf*: string           ## the buffer itself
     input: Stream            ## the input stream
     lineNumber*: int          ## the current line number
     sentinel: int
@@ -40,13 +36,8 @@ type
     offsetBase*: int          # use ``offsetBase + bufpos`` to get the offset
     refillChars: set[char]
 
-const
-  chrSize = sizeof(char)
-
 proc close*(L: var BaseLexer) =
   ## closes the base lexer. This closes `L`'s associated stream too.
-  when not defined(js):
-    dealloc(L.buf)
   close(L.input)
 
 proc fillBuffer(L: var BaseLexer) =
@@ -57,17 +48,21 @@ proc fillBuffer(L: var BaseLexer) =
     oldBufLen: int
   # we know here that pos == L.sentinel, but not if this proc
   # is called the first time by initBaseLexer()
-  assert(L.sentinel < L.bufLen)
-  toCopy = L.bufLen - L.sentinel - 1
+  assert(L.sentinel + 1 <= L.buf.len)
+  toCopy = L.buf.len - (L.sentinel + 1)
   assert(toCopy >= 0)
   if toCopy > 0:
     when defined(js):
-      for i in 0 ..< toCopy: L.buf[i] = L.buf[L.sentinel + 1 + i]
+      for i in 0 ..< toCopy:
+        L.buf[i] = L.buf[L.sentinel + 1 + i]
     else:
-      # "moveMem" handles overlapping regions
-      moveMem(L.buf, addr L.buf[L.sentinel + 1], toCopy * chrSize)
-  charsRead = readData(L.input, addr(L.buf[toCopy]),
-                       (L.sentinel + 1) * chrSize) div chrSize
+      when nimvm:
+        for i in 0 ..< toCopy:
+          L.buf[i] = L.buf[L.sentinel + 1 + i]
+      else:
+        # "moveMem" handles overlapping regions
+        moveMem(addr L.buf[0], addr L.buf[L.sentinel + 1], toCopy)
+  charsRead = L.input.readDataStr(L.buf, toCopy ..< toCopy + L.sentinel + 1)
   s = toCopy + charsRead
   if charsRead < L.sentinel + 1:
     L.buf[s] = EndOfFile      # set end marker
@@ -76,7 +71,7 @@ proc fillBuffer(L: var BaseLexer) =
     # compute sentinel:
     dec(s)                    # BUGFIX (valgrind)
     while true:
-      assert(s < L.bufLen)
+      assert(s < L.buf.len)
       while s >= 0 and L.buf[s] notin L.refillChars: dec(s)
       if s >= 0:
         # we found an appropriate character for a sentinel:
@@ -85,20 +80,14 @@ proc fillBuffer(L: var BaseLexer) =
       else:
         # rather than to give up here because the line is too long,
         # double the buffer's size and try again:
-        oldBufLen = L.bufLen
-        L.bufLen = L.bufLen * 2
-        when defined(js):
-          L.buf.setLen(L.bufLen)
-        else:
-          L.buf = cast[cstring](realloc(L.buf, L.bufLen * chrSize))
-        assert(L.bufLen - oldBufLen == oldBufLen)
-        charsRead = readData(L.input, addr(L.buf[oldBufLen]),
-                             oldBufLen * chrSize) div chrSize
+        oldBufLen = L.buf.len
+        L.buf.setLen(L.buf.len * 2)
+        charsRead = readDataStr(L.input, L.buf, oldBufLen ..< L.buf.len)
         if charsRead < oldBufLen:
           L.buf[oldBufLen + charsRead] = EndOfFile
           L.sentinel = oldBufLen + charsRead
           break
-        s = L.bufLen - 1
+        s = L.buf.len - 1
 
 proc fillBaseLexer(L: var BaseLexer, pos: int): int =
   assert(pos <= L.sentinel)
@@ -148,12 +137,8 @@ proc open*(L: var BaseLexer, input: Stream, bufLen: int = 8192;
   L.input = input
   L.bufpos = 0
   L.offsetBase = 0
-  L.bufLen = bufLen
   L.refillChars = refillChars
-  when defined(js):
-    L.buf = newString(bufLen)
-  else:
-    L.buf = cast[cstring](alloc(bufLen * chrSize))
+  L.buf = newString(bufLen)
   L.sentinel = bufLen - 1
   L.lineStart = 0
   L.lineNumber = 1            # lines start at 1
diff --git a/lib/pure/parsecfg.nim b/lib/pure/parsecfg.nim
index 106d59017..d043cd321 100644
--- a/lib/pure/parsecfg.nim
+++ b/lib/pure/parsecfg.nim
@@ -261,35 +261,32 @@ proc handleCRLF(c: var CfgParser, pos: int): int =
 
 proc getString(c: var CfgParser, tok: var Token, rawMode: bool) =
   var pos = c.bufpos + 1          # skip "
-  var buf = c.buf                 # put `buf` in a register
   tok.kind = tkSymbol
-  if (buf[pos] == '"') and (buf[pos + 1] == '"'):
+  if (c.buf[pos] == '"') and (c.buf[pos + 1] == '"'):
     # long string literal:
     inc(pos, 2)               # skip ""
                               # skip leading newline:
     pos = handleCRLF(c, pos)
-    buf = c.buf
     while true:
-      case buf[pos]
+      case c.buf[pos]
       of '"':
-        if (buf[pos + 1] == '"') and (buf[pos + 2] == '"'): break
+        if (c.buf[pos + 1] == '"') and (c.buf[pos + 2] == '"'): break
         add(tok.literal, '"')
         inc(pos)
       of '\c', '\L':
         pos = handleCRLF(c, pos)
-        buf = c.buf
         add(tok.literal, "\n")
       of lexbase.EndOfFile:
         tok.kind = tkInvalid
         break
       else:
-        add(tok.literal, buf[pos])
+        add(tok.literal, c.buf[pos])
         inc(pos)
     c.bufpos = pos + 3       # skip the three """
   else:
     # ordinary string literal
     while true:
-      var ch = buf[pos]
+      var ch = c.buf[pos]
       if ch == '"':
         inc(pos)              # skip '"'
         break
@@ -307,26 +304,23 @@ proc getString(c: var CfgParser, tok: var Token, rawMode: bool) =
 
 proc getSymbol(c: var CfgParser, tok: var Token) =
   var pos = c.bufpos
-  var buf = c.buf
   while true:
-    add(tok.literal, buf[pos])
+    add(tok.literal, c.buf[pos])
     inc(pos)
-    if not (buf[pos] in SymChars): break
+    if not (c.buf[pos] in SymChars): break
   c.bufpos = pos
   tok.kind = tkSymbol
 
 proc skip(c: var CfgParser) =
   var pos = c.bufpos
-  var buf = c.buf
   while true:
-    case buf[pos]
+    case c.buf[pos]
     of ' ', '\t':
       inc(pos)
     of '#', ';':
-      while not (buf[pos] in {'\c', '\L', lexbase.EndOfFile}): inc(pos)
+      while not (c.buf[pos] in {'\c', '\L', lexbase.EndOfFile}): inc(pos)
     of '\c', '\L':
       pos = handleCRLF(c, pos)
-      buf = c.buf
     else:
       break                   # EndOfFile also leaves the loop
   c.bufpos = pos
diff --git a/lib/pure/parsecsv.nim b/lib/pure/parsecsv.nim
index e0c4f38a4..402e3ad31 100644
--- a/lib/pure/parsecsv.nim
+++ b/lib/pure/parsecsv.nim
@@ -156,44 +156,41 @@ proc open*(my: var CsvParser, filename: string,
 
 proc parseField(my: var CsvParser, a: var string) =
   var pos = my.bufpos
-  var buf = my.buf
   if my.skipWhite:
-    while buf[pos] in {' ', '\t'}: inc(pos)
+    while my.buf[pos] in {' ', '\t'}: inc(pos)
   setLen(a, 0) # reuse memory
-  if buf[pos] == my.quote and my.quote != '\0':
+  if my.buf[pos] == my.quote and my.quote != '\0':
     inc(pos)
     while true:
-      let c = buf[pos]
+      let c = my.buf[pos]
       if c == '\0':
         my.bufpos = pos # can continue after exception?
         error(my, pos, my.quote & " expected")
         break
       elif c == my.quote:
-        if my.esc == '\0' and buf[pos+1] == my.quote:
+        if my.esc == '\0' and my.buf[pos+1] == my.quote:
           add(a, my.quote)
           inc(pos, 2)
         else:
           inc(pos)
           break
       elif c == my.esc:
-        add(a, buf[pos+1])
+        add(a, my.buf[pos+1])
         inc(pos, 2)
       else:
         case c
         of '\c':
           pos = handleCR(my, pos)
-          buf = my.buf
           add(a, "\n")
         of '\l':
           pos = handleLF(my, pos)
-          buf = my.buf
           add(a, "\n")
         else:
           add(a, c)
           inc(pos)
   else:
     while true:
-      let c = buf[pos]
+      let c = my.buf[pos]
       if c == my.sep: break
       if c in {'\c', '\l', '\0'}: break
       add(a, c)
diff --git a/lib/pure/parsejson.nim b/lib/pure/parsejson.nim
index 9c53af6a6..abf2854dd 100644
--- a/lib/pure/parsejson.nim
+++ b/lib/pure/parsejson.nim
@@ -182,11 +182,10 @@ proc parseEscapedUTF16*(buf: cstring, pos: var int): int =
 proc parseString(my: var JsonParser): TokKind =
   result = tkString
   var pos = my.bufpos + 1
-  var buf = my.buf
   if my.rawStringLiterals:
     add(my.a, '"')
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '\0':
       my.err = errQuoteExpected
       result = tkError
@@ -199,9 +198,9 @@ proc parseString(my: var JsonParser): TokKind =
     of '\\':
       if my.rawStringLiterals:
         add(my.a, '\\')
-      case buf[pos+1]
+      case my.buf[pos+1]
       of '\\', '"', '\'', '/':
-        add(my.a, buf[pos+1])
+        add(my.a, my.buf[pos+1])
         inc(pos, 2)
       of 'b':
         add(my.a, '\b')
@@ -223,17 +222,17 @@ proc parseString(my: var JsonParser): TokKind =
           add(my.a, 'u')
         inc(pos, 2)
         var pos2 = pos
-        var r = parseEscapedUTF16(buf, pos)
+        var r = parseEscapedUTF16(my.buf, pos)
         if r < 0:
           my.err = errInvalidToken
           break
         # Deal with surrogates
         if (r and 0xfc00) == 0xd800:
-          if buf[pos] != '\\' or buf[pos+1] != 'u':
+          if my.buf[pos] != '\\' or my.buf[pos+1] != 'u':
             my.err = errInvalidToken
             break
           inc(pos, 2)
-          var s = parseEscapedUTF16(buf, pos)
+          var s = parseEscapedUTF16(my.buf, pos)
           if (s and 0xfc00) == 0xdc00 and s > 0:
             r = 0x10000 + (((r - 0xd800) shl 10) or (s - 0xdc00))
           else:
@@ -242,8 +241,8 @@ proc parseString(my: var JsonParser): TokKind =
         if my.rawStringLiterals:
           let length = pos - pos2
           for i in 1 .. length:
-            if buf[pos2] in {'0'..'9', 'A'..'F', 'a'..'f'}:
-              add(my.a, buf[pos2])
+            if my.buf[pos2] in {'0'..'9', 'A'..'F', 'a'..'f'}:
+              add(my.a, my.buf[pos2])
               inc pos2
             else:
               break
@@ -251,61 +250,54 @@ proc parseString(my: var JsonParser): TokKind =
           add(my.a, toUTF8(Rune(r)))
       else:
         # don't bother with the error
-        add(my.a, buf[pos])
+        add(my.a, my.buf[pos])
         inc(pos)
     of '\c':
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       add(my.a, '\c')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     else:
-      add(my.a, buf[pos])
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos # store back
 
 proc skip(my: var JsonParser) =
   var pos = my.bufpos
-  var buf = my.buf
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '/':
-      if buf[pos+1] == '/':
+      if my.buf[pos+1] == '/':
         # skip line comment:
         inc(pos, 2)
         while true:
-          case buf[pos]
+          case my.buf[pos]
           of '\0':
             break
           of '\c':
             pos = lexbase.handleCR(my, pos)
-            buf = my.buf
             break
           of '\L':
             pos = lexbase.handleLF(my, pos)
-            buf = my.buf
             break
           else:
             inc(pos)
-      elif buf[pos+1] == '*':
+      elif my.buf[pos+1] == '*':
         # skip long comment:
         inc(pos, 2)
         while true:
-          case buf[pos]
+          case my.buf[pos]
           of '\0':
             my.err = errEOC_Expected
             break
           of '\c':
             pos = lexbase.handleCR(my, pos)
-            buf = my.buf
           of '\L':
             pos = lexbase.handleLF(my, pos)
-            buf = my.buf
           of '*':
             inc(pos)
-            if buf[pos] == '/':
+            if my.buf[pos] == '/':
               inc(pos)
               break
           else:
@@ -316,51 +308,47 @@ proc skip(my: var JsonParser) =
       inc(pos)
     of '\c':
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
     else:
       break
   my.bufpos = pos
 
 proc parseNumber(my: var JsonParser) =
   var pos = my.bufpos
-  var buf = my.buf
-  if buf[pos] == '-':
+  if my.buf[pos] == '-':
     add(my.a, '-')
     inc(pos)
-  if buf[pos] == '.':
+  if my.buf[pos] == '.':
     add(my.a, "0.")
     inc(pos)
   else:
-    while buf[pos] in Digits:
-      add(my.a, buf[pos])
+    while my.buf[pos] in Digits:
+      add(my.a, my.buf[pos])
       inc(pos)
-    if buf[pos] == '.':
+    if my.buf[pos] == '.':
       add(my.a, '.')
       inc(pos)
   # digits after the dot:
-  while buf[pos] in Digits:
-    add(my.a, buf[pos])
+  while my.buf[pos] in Digits:
+    add(my.a, my.buf[pos])
     inc(pos)
-  if buf[pos] in {'E', 'e'}:
-    add(my.a, buf[pos])
+  if my.buf[pos] in {'E', 'e'}:
+    add(my.a, my.buf[pos])
     inc(pos)
-    if buf[pos] in {'+', '-'}:
-      add(my.a, buf[pos])
+    if my.buf[pos] in {'+', '-'}:
+      add(my.a, my.buf[pos])
       inc(pos)
-    while buf[pos] in Digits:
-      add(my.a, buf[pos])
+    while my.buf[pos] in Digits:
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
 
 proc parseName(my: var JsonParser) =
   var pos = my.bufpos
-  var buf = my.buf
-  if buf[pos] in IdentStartChars:
-    while buf[pos] in IdentChars:
-      add(my.a, buf[pos])
+  if my.buf[pos] in IdentStartChars:
+    while my.buf[pos] in IdentChars:
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
 
diff --git a/lib/pure/parsesql.nim b/lib/pure/parsesql.nim
index f0961829b..abe712e7f 100644
--- a/lib/pure/parsesql.nim
+++ b/lib/pure/parsesql.nim
@@ -148,35 +148,33 @@ proc handleCRLF(c: var SqlLexer, pos: int): int =
 
 proc skip(c: var SqlLexer) =
   var pos = c.bufpos
-  var buf = c.buf
   var nested = 0
   while true:
-    case buf[pos]
+    case c.buf[pos]
     of ' ', '\t':
       inc(pos)
     of '-':
-      if buf[pos+1] == '-':
-        while not (buf[pos] in {'\c', '\L', lexbase.EndOfFile}): inc(pos)
+      if c.buf[pos+1] == '-':
+        while not (c.buf[pos] in {'\c', '\L', lexbase.EndOfFile}): inc(pos)
       else:
         break
     of '/':
-      if buf[pos+1] == '*':
+      if c.buf[pos+1] == '*':
         inc(pos,2)
         while true:
-          case buf[pos]
+          case c.buf[pos]
           of '\0': break
           of '\c', '\L':
             pos = handleCRLF(c, pos)
-            buf = c.buf
           of '*':
-            if buf[pos+1] == '/':
+            if c.buf[pos+1] == '/':
               inc(pos, 2)
               if nested <= 0: break
               dec(nested)
             else:
               inc(pos)
           of '/':
-            if buf[pos+1] == '*':
+            if c.buf[pos+1] == '*':
               inc(pos, 2)
               inc(nested)
             else:
@@ -185,21 +183,19 @@ proc skip(c: var SqlLexer) =
       else: break
     of '\c', '\L':
       pos = handleCRLF(c, pos)
-      buf = c.buf
     else:
       break                   # EndOfFile also leaves the loop
   c.bufpos = pos
 
 proc getString(c: var SqlLexer, tok: var Token, kind: TokKind) =
   var pos = c.bufpos + 1
-  var buf = c.buf
   tok.kind = kind
   block parseLoop:
     while true:
       while true:
-        var ch = buf[pos]
+        var ch = c.buf[pos]
         if ch == '\'':
-          if buf[pos+1] == '\'':
+          if c.buf[pos+1] == '\'':
             inc(pos, 2)
             add(tok.literal, '\'')
           else:
@@ -221,30 +217,27 @@ proc getString(c: var SqlLexer, tok: var Token, kind: TokKind) =
       if c.lineNumber > line:
         # a new line whitespace has been parsed, so we check if the string
         # continues after the whitespace:
-        buf = c.buf # may have been reallocated
         pos = c.bufpos
-        if buf[pos] == '\'': inc(pos)
+        if c.buf[pos] == '\'': inc(pos)
         else: break parseLoop
       else: break parseLoop
   c.bufpos = pos
 
 proc getDollarString(c: var SqlLexer, tok: var Token) =
   var pos = c.bufpos + 1
-  var buf = c.buf
   tok.kind = tkDollarQuotedConstant
   var tag = "$"
-  while buf[pos] in IdentChars:
-    add(tag, buf[pos])
+  while c.buf[pos] in IdentChars:
+    add(tag, c.buf[pos])
     inc(pos)
-  if buf[pos] == '$': inc(pos)
+  if c.buf[pos] == '$': inc(pos)
   else:
     tok.kind = tkInvalid
     return
   while true:
-    case buf[pos]
+    case c.buf[pos]
     of '\c', '\L':
       pos = handleCRLF(c, pos)
-      buf = c.buf
       add(tok.literal, "\L")
     of '\0':
       tok.kind = tkInvalid
@@ -252,37 +245,35 @@ proc getDollarString(c: var SqlLexer, tok: var Token) =
     of '$':
       inc(pos)
       var tag2 = "$"
-      while buf[pos] in IdentChars:
-        add(tag2, buf[pos])
+      while c.buf[pos] in IdentChars:
+        add(tag2, c.buf[pos])
         inc(pos)
-      if buf[pos] == '$': inc(pos)
+      if c.buf[pos] == '$': inc(pos)
       if tag2 == tag: break
       add(tok.literal, tag2)
       add(tok.literal, '$')
     else:
-      add(tok.literal, buf[pos])
+      add(tok.literal, c.buf[pos])
       inc(pos)
   c.bufpos = pos
 
 proc getSymbol(c: var SqlLexer, tok: var Token) =
   var pos = c.bufpos
-  var buf = c.buf
   while true:
-    add(tok.literal, buf[pos])
+    add(tok.literal, c.buf[pos])
     inc(pos)
-    if buf[pos] notin {'a'..'z','A'..'Z','0'..'9','_','$', '\128'..'\255'}:
+    if c.buf[pos] notin {'a'..'z','A'..'Z','0'..'9','_','$', '\128'..'\255'}:
       break
   c.bufpos = pos
   tok.kind = tkIdentifier
 
 proc getQuotedIdentifier(c: var SqlLexer, tok: var Token, quote='\"') =
   var pos = c.bufpos + 1
-  var buf = c.buf
   tok.kind = tkQuotedIdentifier
   while true:
-    var ch = buf[pos]
+    var ch = c.buf[pos]
     if ch == quote:
-      if buf[pos+1] == quote:
+      if c.buf[pos+1] == quote:
         inc(pos, 2)
         add(tok.literal, quote)
       else:
@@ -298,11 +289,10 @@ proc getQuotedIdentifier(c: var SqlLexer, tok: var Token, quote='\"') =
 
 proc getBitHexString(c: var SqlLexer, tok: var Token, validChars: set[char]) =
   var pos = c.bufpos + 1
-  var buf = c.buf
   block parseLoop:
     while true:
       while true:
-        var ch = buf[pos]
+        var ch = c.buf[pos]
         if ch in validChars:
           add(tok.literal, ch)
           inc(pos)
@@ -318,9 +308,8 @@ proc getBitHexString(c: var SqlLexer, tok: var Token, validChars: set[char]) =
       if c.lineNumber > line:
         # a new line whitespace has been parsed, so we check if the string
         # continues after the whitespace:
-        buf = c.buf # may have been reallocated
         pos = c.bufpos
-        if buf[pos] == '\'': inc(pos)
+        if c.buf[pos] == '\'': inc(pos)
         else: break parseLoop
       else: break parseLoop
   c.bufpos = pos
@@ -328,29 +317,28 @@ proc getBitHexString(c: var SqlLexer, tok: var Token, validChars: set[char]) =
 proc getNumeric(c: var SqlLexer, tok: var Token) =
   tok.kind = tkInteger
   var pos = c.bufpos
-  var buf = c.buf
-  while buf[pos] in Digits:
-    add(tok.literal, buf[pos])
+  while c.buf[pos] in Digits:
+    add(tok.literal, c.buf[pos])
     inc(pos)
-  if buf[pos] == '.':
+  if c.buf[pos] == '.':
     tok.kind = tkNumeric
-    add(tok.literal, buf[pos])
+    add(tok.literal, c.buf[pos])
     inc(pos)
-    while buf[pos] in Digits:
-      add(tok.literal, buf[pos])
+    while c.buf[pos] in Digits:
+      add(tok.literal, c.buf[pos])
       inc(pos)
-  if buf[pos] in {'E', 'e'}:
+  if c.buf[pos] in {'E', 'e'}:
     tok.kind = tkNumeric
-    add(tok.literal, buf[pos])
+    add(tok.literal, c.buf[pos])
     inc(pos)
-    if buf[pos] == '+':
+    if c.buf[pos] == '+':
       inc(pos)
-    elif buf[pos] == '-':
-      add(tok.literal, buf[pos])
+    elif c.buf[pos] == '-':
+      add(tok.literal, c.buf[pos])
       inc(pos)
-    if buf[pos] in Digits:
-      while buf[pos] in Digits:
-        add(tok.literal, buf[pos])
+    if c.buf[pos] in Digits:
+      while c.buf[pos] in Digits:
+        add(tok.literal, c.buf[pos])
         inc(pos)
     else:
       tok.kind = tkInvalid
@@ -361,24 +349,23 @@ proc getOperator(c: var SqlLexer, tok: var Token) =
                      '^', '&', '|', '`', '?'}
   tok.kind = tkOperator
   var pos = c.bufpos
-  var buf = c.buf
   var trailingPlusMinus = false
   while true:
-    case buf[pos]
+    case c.buf[pos]
     of '-':
-      if buf[pos] == '-': break
-      if not trailingPlusMinus and buf[pos+1] notin operators and
+      if c.buf[pos] == '-': break
+      if not trailingPlusMinus and c.buf[pos+1] notin operators and
            tok.literal.len > 0: break
     of '/':
-      if buf[pos] == '*': break
+      if c.buf[pos] == '*': break
     of '~', '!', '@', '#', '%', '^', '&', '|', '`', '?':
       trailingPlusMinus = true
     of '+':
-      if not trailingPlusMinus and buf[pos+1] notin operators and
+      if not trailingPlusMinus and c.buf[pos+1] notin operators and
            tok.literal.len > 0: break
     of '*', '<', '>', '=': discard
     else: break
-    add(tok.literal, buf[pos])
+    add(tok.literal, c.buf[pos])
     inc(pos)
   c.bufpos = pos
 
diff --git a/lib/pure/parsexml.nim b/lib/pure/parsexml.nim
index 953c5cdde..3b77f9c62 100644
--- a/lib/pure/parsexml.nim
+++ b/lib/pure/parsexml.nim
@@ -345,11 +345,10 @@ proc markError(my: var XmlParser, kind: XmlErrorKind) {.inline.} =
 
 proc parseCDATA(my: var XmlParser) =
   var pos = my.bufpos + len("<![CDATA[")
-  var buf = my.buf
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of ']':
-      if buf[pos+1] == ']' and buf[pos+2] == '>':
+      if my.buf[pos+1] == ']' and my.buf[pos+2] == '>':
         inc(pos, 3)
         break
       add(my.a, ']')
@@ -359,29 +358,25 @@ proc parseCDATA(my: var XmlParser) =
       break
     of '\c':
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     of '/':
       pos = lexbase.handleRefillChar(my, pos)
-      buf = my.buf
       add(my.a, '/')
     else:
-      add(my.a, buf[pos])
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos # store back
   my.kind = xmlCData
 
 proc parseComment(my: var XmlParser) =
   var pos = my.bufpos + len("<!--")
-  var buf = my.buf
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '-':
-      if buf[pos+1] == '-' and buf[pos+2] == '>':
+      if my.buf[pos+1] == '-' and my.buf[pos+2] == '>':
         inc(pos, 3)
         break
       if my.options.contains(reportComments): add(my.a, '-')
@@ -391,38 +386,32 @@ proc parseComment(my: var XmlParser) =
       break
     of '\c':
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       if my.options.contains(reportComments): add(my.a, '\L')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       if my.options.contains(reportComments): add(my.a, '\L')
     of '/':
       pos = lexbase.handleRefillChar(my, pos)
-      buf = my.buf
       if my.options.contains(reportComments): add(my.a, '/')
     else:
-      if my.options.contains(reportComments): add(my.a, buf[pos])
+      if my.options.contains(reportComments): add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
   my.kind = xmlComment
 
 proc parseWhitespace(my: var XmlParser, skip=false) =
   var pos = my.bufpos
-  var buf = my.buf
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of ' ', '\t':
-      if not skip: add(my.a, buf[pos])
+      if not skip: add(my.a, my.buf[pos])
       inc(pos)
     of '\c':
       # the specification says that CR-LF, CR are to be transformed to LF
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       if not skip: add(my.a, '\L')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       if not skip: add(my.a, '\L')
     else:
       break
@@ -434,53 +423,51 @@ const
 
 proc parseName(my: var XmlParser, dest: var string) =
   var pos = my.bufpos
-  var buf = my.buf
-  if buf[pos] in NameStartChar:
+  if my.buf[pos] in NameStartChar:
     while true:
-      add(dest, buf[pos])
+      add(dest, my.buf[pos])
       inc(pos)
-      if buf[pos] notin NameChar: break
+      if my.buf[pos] notin NameChar: break
     my.bufpos = pos
   else:
     markError(my, errNameExpected)
 
 proc parseEntity(my: var XmlParser, dest: var string) =
   var pos = my.bufpos+1
-  var buf = my.buf
   my.kind = xmlCharData
-  if buf[pos] == '#':
+  if my.buf[pos] == '#':
     var r: int
     inc(pos)
-    if buf[pos] == 'x':
+    if my.buf[pos] == 'x':
       inc(pos)
       while true:
-        case buf[pos]
-        of '0'..'9': r = (r shl 4) or (ord(buf[pos]) - ord('0'))
-        of 'a'..'f': r = (r shl 4) or (ord(buf[pos]) - ord('a') + 10)
-        of 'A'..'F': r = (r shl 4) or (ord(buf[pos]) - ord('A') + 10)
+        case my.buf[pos]
+        of '0'..'9': r = (r shl 4) or (ord(my.buf[pos]) - ord('0'))
+        of 'a'..'f': r = (r shl 4) or (ord(my.buf[pos]) - ord('a') + 10)
+        of 'A'..'F': r = (r shl 4) or (ord(my.buf[pos]) - ord('A') + 10)
         else: break
         inc(pos)
     else:
-      while buf[pos] in {'0'..'9'}:
-        r = r * 10 + (ord(buf[pos]) - ord('0'))
+      while my.buf[pos] in {'0'..'9'}:
+        r = r * 10 + (ord(my.buf[pos]) - ord('0'))
         inc(pos)
     add(dest, toUTF8(Rune(r)))
-  elif buf[pos] == 'l' and buf[pos+1] == 't' and buf[pos+2] == ';':
+  elif my.buf[pos] == 'l' and my.buf[pos+1] == 't' and my.buf[pos+2] == ';':
     add(dest, '<')
     inc(pos, 2)
-  elif buf[pos] == 'g' and buf[pos+1] == 't' and buf[pos+2] == ';':
+  elif my.buf[pos] == 'g' and my.buf[pos+1] == 't' and my.buf[pos+2] == ';':
     add(dest, '>')
     inc(pos, 2)
-  elif buf[pos] == 'a' and buf[pos+1] == 'm' and buf[pos+2] == 'p' and
-      buf[pos+3] == ';':
+  elif my.buf[pos] == 'a' and my.buf[pos+1] == 'm' and my.buf[pos+2] == 'p' and
+      my.buf[pos+3] == ';':
     add(dest, '&')
     inc(pos, 3)
-  elif buf[pos] == 'a' and buf[pos+1] == 'p' and buf[pos+2] == 'o' and
-      buf[pos+3] == 's' and buf[pos+4] == ';':
+  elif my.buf[pos] == 'a' and my.buf[pos+1] == 'p' and my.buf[pos+2] == 'o' and
+      my.buf[pos+3] == 's' and my.buf[pos+4] == ';':
     add(dest, '\'')
     inc(pos, 4)
-  elif buf[pos] == 'q' and buf[pos+1] == 'u' and buf[pos+2] == 'o' and
-      buf[pos+3] == 't' and buf[pos+4] == ';':
+  elif my.buf[pos] == 'q' and my.buf[pos+1] == 'u' and my.buf[pos+2] == 'o' and
+      my.buf[pos+3] == 't' and my.buf[pos+4] == ';':
     add(dest, '"')
     inc(pos, 4)
   else:
@@ -491,7 +478,7 @@ proc parseEntity(my: var XmlParser, dest: var string) =
       my.kind = xmlEntity
     else:
       add(dest, '&')
-  if buf[pos] == ';':
+  if my.buf[pos] == ';':
     inc(pos)
   else:
     markError(my, errSemicolonExpected)
@@ -501,15 +488,14 @@ proc parsePI(my: var XmlParser) =
   inc(my.bufpos, "<?".len)
   parseName(my, my.a)
   var pos = my.bufpos
-  var buf = my.buf
   setLen(my.b, 0)
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '\0':
       markError(my, errQmGtExpected)
       break
     of '?':
-      if buf[pos+1] == '>':
+      if my.buf[pos+1] == '>':
         inc(pos, 2)
         break
       add(my.b, '?')
@@ -517,18 +503,15 @@ proc parsePI(my: var XmlParser) =
     of '\c':
       # the specification says that CR-LF, CR are to be transformed to LF
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       add(my.b, '\L')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       add(my.b, '\L')
     of '/':
       pos = lexbase.handleRefillChar(my, pos)
-      buf = my.buf
       add(my.b, '/')
     else:
-      add(my.b, buf[pos])
+      add(my.b, my.buf[pos])
       inc(pos)
   my.bufpos = pos
   my.kind = xmlPI
@@ -536,10 +519,9 @@ proc parsePI(my: var XmlParser) =
 proc parseSpecial(my: var XmlParser) =
   # things that start with <!
   var pos = my.bufpos + 2
-  var buf = my.buf
   var opentags = 0
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '\0':
       markError(my, errGtExpected)
       break
@@ -556,18 +538,15 @@ proc parseSpecial(my: var XmlParser) =
       add(my.a, '>')
     of '\c':
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     of '/':
       pos = lexbase.handleRefillChar(my, pos)
-      buf = my.buf
       add(my.b, '/')
     else:
-      add(my.a, buf[pos])
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
   my.kind = xmlSpecial
@@ -635,13 +614,12 @@ proc parseAttribute(my: var XmlParser) =
   parseWhitespace(my, skip=true)
 
   var pos = my.bufpos
-  var buf = my.buf
-  if buf[pos] in {'\'', '"'}:
-    var quote = buf[pos]
+  if my.buf[pos] in {'\'', '"'}:
+    var quote = my.buf[pos]
     var pendingSpace = false
     inc(pos)
     while true:
-      case buf[pos]
+      case my.buf[pos]
       of '\0':
         markError(my, errQuoteExpected)
         break
@@ -658,31 +636,28 @@ proc parseAttribute(my: var XmlParser) =
         inc(pos)
       of '\c':
         pos = lexbase.handleCR(my, pos)
-        buf = my.buf
         pendingSpace = true
       of '\L':
         pos = lexbase.handleLF(my, pos)
-        buf = my.buf
         pendingSpace = true
       of '/':
         pos = lexbase.handleRefillChar(my, pos)
-        buf = my.buf
         add(my.b, '/')
       else:
-        if buf[pos] == quote:
+        if my.buf[pos] == quote:
           inc(pos)
           break
         else:
           if pendingSpace:
             add(my.b, ' ')
             pendingSpace = false
-          add(my.b, buf[pos])
+          add(my.b, my.buf[pos])
           inc(pos)
   elif allowUnquotedAttribs in my.options:
     const disallowedChars = {'"', '\'', '`', '=', '<', '>', ' ',
                              '\0', '\t', '\L', '\F', '\f'}
     let startPos = pos
-    while (let c = buf[pos]; c notin disallowedChars):
+    while (let c = my.buf[pos]; c notin disallowedChars):
       if c == '&':
         my.bufpos = pos
         parseEntity(my, my.b)
@@ -696,33 +671,29 @@ proc parseAttribute(my: var XmlParser) =
   else:
     markError(my, errQuoteExpected)
     # error corrections: guess what was meant
-    while buf[pos] != '>' and buf[pos] > ' ':
-      add(my.b, buf[pos])
+    while my.buf[pos] != '>' and my.buf[pos] > ' ':
+      add(my.b, my.buf[pos])
       inc pos
   my.bufpos = pos
   parseWhitespace(my, skip=true)
 
 proc parseCharData(my: var XmlParser) =
   var pos = my.bufpos
-  var buf = my.buf
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '\0', '<', '&': break
     of '\c':
       # the specification says that CR-LF, CR are to be transformed to LF
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     of '/':
       pos = lexbase.handleRefillChar(my, pos)
-      buf = my.buf
       add(my.a, '/')
     else:
-      add(my.a, buf[pos])
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
   my.kind = xmlCharData
@@ -731,18 +702,17 @@ proc rawGetTok(my: var XmlParser) =
   my.kind = xmlError
   setLen(my.a, 0)
   var pos = my.bufpos
-  var buf = my.buf
-  case buf[pos]
+  case my.buf[pos]
   of '<':
-    case buf[pos+1]
+    case my.buf[pos+1]
     of '/':
       parseEndTag(my)
     of '!':
-      if buf[pos+2] == '[' and buf[pos+3] == 'C' and buf[pos+4] == 'D' and
-          buf[pos+5] == 'A' and buf[pos+6] == 'T' and buf[pos+7] == 'A' and
-          buf[pos+8] == '[':
+      if my.buf[pos+2] == '[' and my.buf[pos+3] == 'C' and my.buf[pos+4] == 'D' and
+          my.buf[pos+5] == 'A' and my.buf[pos+6] == 'T' and my.buf[pos+7] == 'A' and
+          my.buf[pos+8] == '[':
         parseCDATA(my)
-      elif buf[pos+2] == '-' and buf[pos+3] == '-':
+      elif my.buf[pos+2] == '-' and my.buf[pos+3] == '-':
         parseComment(my)
       else:
         parseSpecial(my)
@@ -841,4 +811,3 @@ when not defined(testing) and isMainModule:
     of xmlSpecial:
       echo("SPECIAL: " & x.charData)
   close(x)
-
diff --git a/lib/pure/pegs.nim b/lib/pure/pegs.nim
index 957091918..644de6007 100644
--- a/lib/pure/pegs.nim
+++ b/lib/pure/pegs.nim
@@ -1545,20 +1545,17 @@ proc getEscapedChar(c: var PegLexer, tok: var Token) =
 
 proc skip(c: var PegLexer) =
   var pos = c.bufpos
-  var buf = c.buf
   while pos < c.buf.len:
-    case buf[pos]
+    case c.buf[pos]
     of ' ', '\t':
       inc(pos)
     of '#':
       while (pos < c.buf.len) and
-             not (buf[pos] in {'\c', '\L', '\0'}): inc(pos)
+             not (c.buf[pos] in {'\c', '\L', '\0'}): inc(pos)
     of '\c':
       pos = handleCR(c, pos)
-      buf = c.buf
     of '\L':
       pos = handleLF(c, pos)
-      buf = c.buf
     else:
       break                   # EndOfFile also leaves the loop
   c.bufpos = pos
@@ -1566,10 +1563,9 @@ proc skip(c: var PegLexer) =
 proc getString(c: var PegLexer, tok: var Token) =
   tok.kind = tkStringLit
   var pos = c.bufpos + 1
-  var buf = c.buf
-  var quote = buf[pos-1]
+  var quote = c.buf[pos-1]
   while pos < c.buf.len:
-    case buf[pos]
+    case c.buf[pos]
     of '\\':
       c.bufpos = pos
       getEscapedChar(c, tok)
@@ -1577,22 +1573,21 @@ proc getString(c: var PegLexer, tok: var Token) =
     of '\c', '\L', '\0':
       tok.kind = tkInvalid
       break
-    elif buf[pos] == quote:
+    elif c.buf[pos] == quote:
       inc(pos)
       break
     else:
-      add(tok.literal, buf[pos])
+      add(tok.literal, c.buf[pos])
       inc(pos)
   c.bufpos = pos
 
 proc getDollar(c: var PegLexer, tok: var Token) =
   var pos = c.bufpos + 1
-  var buf = c.buf
-  if buf[pos] in {'0'..'9'}:
+  if c.buf[pos] in {'0'..'9'}:
     tok.kind = tkBackref
     tok.index = 0
-    while pos < c.buf.len and buf[pos] in {'0'..'9'}:
-      tok.index = tok.index * 10 + ord(buf[pos]) - ord('0')
+    while pos < c.buf.len and c.buf[pos] in {'0'..'9'}:
+      tok.index = tok.index * 10 + ord(c.buf[pos]) - ord('0')
       inc(pos)
   else:
     tok.kind = tkDollar
@@ -1602,14 +1597,13 @@ proc getCharSet(c: var PegLexer, tok: var Token) =
   tok.kind = tkCharSet
   tok.charset = {}
   var pos = c.bufpos + 1
-  var buf = c.buf
   var caret = false
-  if buf[pos] == '^':
+  if c.buf[pos] == '^':
     inc(pos)
     caret = true
   while pos < c.buf.len:
     var ch: char
-    case buf[pos]
+    case c.buf[pos]
     of ']':
       if pos < c.buf.len: inc(pos)
       break
@@ -1622,11 +1616,11 @@ proc getCharSet(c: var PegLexer, tok: var Token) =
       tok.kind = tkInvalid
       break
     else:
-      ch = buf[pos]
+      ch = c.buf[pos]
       inc(pos)
     incl(tok.charset, ch)
-    if buf[pos] == '-':
-      if pos+1 < c.buf.len and buf[pos+1] == ']':
+    if c.buf[pos] == '-':
+      if pos+1 < c.buf.len and c.buf[pos+1] == ']':
         incl(tok.charset, '-')
         inc(pos)
       else:
@@ -1635,7 +1629,7 @@ proc getCharSet(c: var PegLexer, tok: var Token) =
         else:
           break
         var ch2: char
-        case buf[pos]
+        case c.buf[pos]
         of '\\':
           c.bufpos = pos
           getEscapedChar(c, tok)
@@ -1646,7 +1640,7 @@ proc getCharSet(c: var PegLexer, tok: var Token) =
           break
         else:
           if pos+1 < c.buf.len:
-            ch2 = buf[pos]
+            ch2 = c.buf[pos]
             inc(pos)
           else:
             break
@@ -1657,11 +1651,10 @@ proc getCharSet(c: var PegLexer, tok: var Token) =
 
 proc getSymbol(c: var PegLexer, tok: var Token) =
   var pos = c.bufpos
-  var buf = c.buf
   while pos < c.buf.len:
-    add(tok.literal, buf[pos])
+    add(tok.literal, c.buf[pos])
     inc(pos)
-    if pos < buf.len and buf[pos] notin strutils.IdentChars: break
+    if pos < c.buf.len and c.buf[pos] notin strutils.IdentChars: break
   c.bufpos = pos
   tok.kind = tkIdentifier
 
diff --git a/lib/pure/streams.nim b/lib/pure/streams.nim
index 0f65d6c0e..6c69a9bb6 100644
--- a/lib/pure/streams.nim
+++ b/lib/pure/streams.nim
@@ -53,12 +53,17 @@ type
       {.nimcall, raises: [Defect, IOError, OSError], tags: [], gcsafe.}
     getPositionImpl*: proc (s: Stream): int
       {.nimcall, raises: [Defect, IOError, OSError], tags: [], gcsafe.}
+
+    readDataStrImpl*: proc (s: Stream, buffer: var string, slice: Slice[int]): int
+      {.nimcall, raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
+
     readDataImpl*: proc (s: Stream, buffer: pointer, bufLen: int): int
       {.nimcall, raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
     peekDataImpl*: proc (s: Stream, buffer: pointer, bufLen: int): int
       {.nimcall, raises: [Defect, IOError, OSError], tags: [ReadIOEffect], gcsafe.}
     writeDataImpl*: proc (s: Stream, buffer: pointer, bufLen: int)
-      {.nimcall, raises: [Defect, IOError, OSError], tags: [WriteIOEffect], gcsafe.}
+        {.nimcall, raises: [Defect, IOError, OSError], tags: [WriteIOEffect], gcsafe.}
+
     flushImpl*: proc (s: Stream)
       {.nimcall, raises: [Defect, IOError, OSError], tags: [WriteIOEffect], gcsafe.}
 
@@ -87,6 +92,14 @@ proc readData*(s: Stream, buffer: pointer, bufLen: int): int =
   ## low level proc that reads data into an untyped `buffer` of `bufLen` size.
   result = s.readDataImpl(s, buffer, bufLen)
 
+proc readDataStr*(s: Stream, buffer: var string, slice: Slice[int]): int =
+  ## low level proc that reads data into a string ``buffer`` at ``slice``.
+  if s.readDataStrImpl != nil:
+    result = s.readDataStrImpl(s, buffer, slice)
+  else:
+    # fallback
+    result = s.readData(addr buffer[0], buffer.len)
+
 when not defined(js):
   proc readAll*(s: Stream): string =
     ## Reads all available data.
@@ -344,6 +357,19 @@ when not defined(js):
     var s = StringStream(s)
     return s.pos
 
+  proc ssReadDataStr(s: Stream, buffer: var string, slice: Slice[int]): int =
+    var s = StringStream(s)
+    result = min(slice.b + 1 - slice.a, s.data.len - s.pos)
+    if result > 0:
+      when nimvm:
+        for i in 0 ..< result: # sorry, but no fast string splicing on the vm.
+          buffer[slice.a + i] = s.data[s.pos + i]
+      else:
+        copyMem(unsafeAddr buffer[slice.a], addr s.data[s.pos], result)
+      inc(s.pos, result)
+    else:
+      result = 0
+
   proc ssReadData(s: Stream, buffer: pointer, bufLen: int): int =
     var s = StringStream(s)
     result = min(bufLen, s.data.len - s.pos)
@@ -389,6 +415,7 @@ when not defined(js):
     result.readDataImpl = ssReadData
     result.peekDataImpl = ssPeekData
     result.writeDataImpl = ssWriteData
+    result.readDataStrImpl = ssReadDataStr
 
   type
     FileStream* = ref FileStreamObj ## a stream that encapsulates a `File`
@@ -407,6 +434,9 @@ when not defined(js):
   proc fsReadData(s: Stream, buffer: pointer, bufLen: int): int =
     result = readBuffer(FileStream(s).f, buffer, bufLen)
 
+  proc fsReadDataStr(s: Stream, buffer: var string, slice: Slice[int]): int =
+    result = readBuffer(FileStream(s).f, addr buffer[slice.a], slice.b + 1 - slice.a)
+
   proc fsPeekData(s: Stream, buffer: pointer, bufLen: int): int =
     let pos = fsGetPosition(s)
     defer: fsSetPosition(s, pos)
@@ -424,6 +454,7 @@ when not defined(js):
     result.atEndImpl = fsAtEnd
     result.setPositionImpl = fsSetPosition
     result.getPositionImpl = fsGetPosition
+    result.readDataStrImpl = fsReadDataStr
     result.readDataImpl = fsReadData
     result.peekDataImpl = fsPeekData
     result.writeDataImpl = fsWriteData
diff --git a/nimsuggest/sexp.nim b/nimsuggest/sexp.nim
index 8f92e9098..910ecb9e9 100644
--- a/nimsuggest/sexp.nim
+++ b/nimsuggest/sexp.nim
@@ -124,9 +124,8 @@ proc handleHexChar(c: char, x: var int): bool =
 proc parseString(my: var SexpParser): TTokKind =
   result = tkString
   var pos = my.bufpos + 1
-  var buf = my.buf
   while true:
-    case buf[pos]
+    case my.buf[pos]
     of '\0':
       my.err = errQuoteExpected
       result = tkError
@@ -135,9 +134,9 @@ proc parseString(my: var SexpParser): TTokKind =
       inc(pos)
       break
     of '\\':
-      case buf[pos+1]
+      case my.buf[pos+1]
       of '\\', '"', '\'', '/':
-        add(my.a, buf[pos+1])
+        add(my.a, my.buf[pos+1])
         inc(pos, 2)
       of 'b':
         add(my.a, '\b')
@@ -157,65 +156,61 @@ proc parseString(my: var SexpParser): TTokKind =
       of 'u':
         inc(pos, 2)
         var r: int
-        if handleHexChar(buf[pos], r): inc(pos)
-        if handleHexChar(buf[pos], r): inc(pos)
-        if handleHexChar(buf[pos], r): inc(pos)
-        if handleHexChar(buf[pos], r): inc(pos)
+        if handleHexChar(my.buf[pos], r): inc(pos)
+        if handleHexChar(my.buf[pos], r): inc(pos)
+        if handleHexChar(my.buf[pos], r): inc(pos)
+        if handleHexChar(my.buf[pos], r): inc(pos)
         add(my.a, toUTF8(Rune(r)))
       else:
         # don't bother with the error
-        add(my.a, buf[pos])
+        add(my.a, my.buf[pos])
         inc(pos)
     of '\c':
       pos = lexbase.handleCR(my, pos)
-      buf = my.buf
       add(my.a, '\c')
     of '\L':
       pos = lexbase.handleLF(my, pos)
-      buf = my.buf
       add(my.a, '\L')
     else:
-      add(my.a, buf[pos])
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos # store back
 
 proc parseNumber(my: var SexpParser) =
   var pos = my.bufpos
-  var buf = my.buf
-  if buf[pos] == '-':
+  if my.buf[pos] == '-':
     add(my.a, '-')
     inc(pos)
-  if buf[pos] == '.':
+  if my.buf[pos] == '.':
     add(my.a, "0.")
     inc(pos)
   else:
-    while buf[pos] in Digits:
-      add(my.a, buf[pos])
+    while my.buf[pos] in Digits:
+      add(my.a, my.buf[pos])
       inc(pos)
-    if buf[pos] == '.':
+    if my.buf[pos] == '.':
       add(my.a, '.')
       inc(pos)
   # digits after the dot:
-  while buf[pos] in Digits:
-    add(my.a, buf[pos])
+  while my.buf[pos] in Digits:
+    add(my.a, my.buf[pos])
     inc(pos)
-  if buf[pos] in {'E', 'e'}:
-    add(my.a, buf[pos])
+  if my.buf[pos] in {'E', 'e'}:
+    add(my.a, my.buf[pos])
     inc(pos)
-    if buf[pos] in {'+', '-'}:
-      add(my.a, buf[pos])
+    if my.buf[pos] in {'+', '-'}:
+      add(my.a, my.buf[pos])
       inc(pos)
-    while buf[pos] in Digits:
-      add(my.a, buf[pos])
+    while my.buf[pos] in Digits:
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
 
 proc parseSymbol(my: var SexpParser) =
   var pos = my.bufpos
-  var buf = my.buf
-  if buf[pos] in IdentStartChars:
-    while buf[pos] in IdentChars:
-      add(my.a, buf[pos])
+  if my.buf[pos] in IdentStartChars:
+    while my.buf[pos] in IdentChars:
+      add(my.a, my.buf[pos])
       inc(pos)
   my.bufpos = pos
 
diff --git a/tests/stdlib/tjsonmacro.nim b/tests/stdlib/tjsonmacro.nim
index 2e95b4833..32493f9bc 100644
--- a/tests/stdlib/tjsonmacro.nim
+++ b/tests/stdlib/tjsonmacro.nim
@@ -520,3 +520,43 @@ when true:
     block test_tuple:
       doAssert $(%* (a1: 10, a2: "foo")) == """{"a1":10,"a2":"foo"}"""
       doAssert $(%* (10, "foo")) == """[10,"foo"]"""
+
+# TODO: when the issue with the limeted vm registers is solved, the
+# exact same test as above should be evaluated at compile time as
+# well, to ensure that the vm functionality won't diverge from the
+# runtime functionality. Until then, the following test should do it.
+
+static:
+  var t = parseJson("""
+    {
+      "name":"Bongo",
+      "email":"bongo@bingo.com",
+      "list": [11,7,15],
+      "year": 1975,
+      "dict": {"a": 1, "b": 2},
+      "arr": [1.0, 2.0, 7.0],
+      "person": {"name": "boney"},
+      "dog": {"name": "honey"},
+      "fruit": {"color": 10},
+      "distfruit": {"color": 11},
+      "emails": ["abc", "123"]
+    }
+  """)
+
+  doAssert t["name"].getStr == "Bongo"
+  doAssert t["email"].getStr == "bongo@bingo.com"
+  doAssert t["list"][0].getInt == 11
+  doAssert t["list"][1].getInt == 7
+  doAssert t["list"][2].getInt == 15
+  doAssert t["year"].getInt == 1975
+  doAssert t["dict"]["a"].getInt == 1
+  doAssert t["dict"]["b"].getInt == 2
+  doAssert t["arr"][0].getFloat == 1.0
+  doAssert t["arr"][1].getFloat == 2.0
+  doAssert t["arr"][2].getFloat == 7.0
+  doAssert t["person"]["name"].getStr == "boney"
+  doAssert t["distfruit"]["color"].getInt == 11
+  doAssert t["dog"]["name"].getStr == "honey"
+  doAssert t["fruit"]["color"].getInt == 10
+  doAssert t["emails"][0].getStr == "abc"
+  doAssert t["emails"][1].getStr == "123"