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#
#
# The Nim Compiler
# (c) Copyright 2012 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# Base Object of a lexer with efficient buffer handling. In fact
# I believe that this is the most efficient method of buffer
# handling that exists! Only at line endings checks are necessary
# if the buffer needs refilling.
import
llstream, strutils
const
Lrz* = ' '
Apo* = '\''
Tabulator* = '\x09'
ESC* = '\x1B'
CR* = '\x0D'
FF* = '\x0C'
LF* = '\x0A'
BEL* = '\x07'
BACKSPACE* = '\x08'
VT* = '\x0B'
const
EndOfFile* = '\0' # end of file marker
# A little picture makes everything clear :-)
# buf:
# "Example Text\n ha!" bufLen = 17
# ^pos = 0 ^ sentinel = 12
#
NewLines* = {CR, LF}
type
TBaseLexer* = object of RootObj
bufpos*: int
buf*: string
stream*: PLLStream # we read from this stream
lineNumber*: int # the current line number
# private data:
sentinel*: int
lineStart*: int # index of last line start in buffer
offsetBase*: int # use ``offsetBase + bufpos`` to get the offset
proc openBaseLexer*(L: var TBaseLexer, inputstream: PLLStream,
bufLen: int = 8192)
# 8K is a reasonable buffer size
proc closeBaseLexer*(L: var TBaseLexer)
proc getCurrentLine*(L: TBaseLexer, marker: bool = true): string
proc getColNumber*(L: TBaseLexer, pos: int): int
proc handleCR*(L: var TBaseLexer, pos: int): int
# Call this if you scanned over CR in the buffer; it returns the
# position to continue the scanning from. `pos` must be the position
# of the CR.
proc handleLF*(L: var TBaseLexer, pos: int): int
# Call this if you scanned over LF in the buffer; it returns the the
# position to continue the scanning from. `pos` must be the position
# of the LF.
# implementation
proc closeBaseLexer(L: var TBaseLexer) =
llStreamClose(L.stream)
proc fillBuffer(L: var TBaseLexer) =
var
charsRead, toCopy, s: int # all are in characters,
# not bytes (in case this
# is not the same)
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.buf.len)
toCopy = L.buf.len - L.sentinel - 1
assert(toCopy >= 0)
if toCopy > 0:
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)
s = toCopy + charsRead
if charsRead < L.sentinel + 1:
L.buf[s] = EndOfFile # set end marker
L.sentinel = s
else:
# compute sentinel:
dec(s) # BUGFIX (valgrind)
while true:
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:
L.sentinel = s
break
else:
# rather than to give up here because the line is too long,
# double the buffer's size and try again:
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)
if charsRead < oldBufLen:
L.buf[oldBufLen + charsRead] = EndOfFile
L.sentinel = oldBufLen + charsRead
break
s = L.buf.len - 1
proc fillBaseLexer(L: var TBaseLexer, pos: int): int =
assert(pos <= L.sentinel)
if pos < L.sentinel:
result = pos + 1 # nothing to do
else:
fillBuffer(L)
L.offsetBase += pos + 1
L.bufpos = 0
result = 0
L.lineStart = result
proc handleCR(L: var TBaseLexer, pos: int): int =
assert(L.buf[pos] == CR)
inc(L.lineNumber)
result = fillBaseLexer(L, pos)
if L.buf[result] == LF:
result = fillBaseLexer(L, result)
proc handleLF(L: var TBaseLexer, pos: int): int =
assert(L.buf[pos] == LF)
inc(L.lineNumber)
result = fillBaseLexer(L, pos) #L.lastNL := result-1; // BUGFIX: was: result;
proc skipUTF8BOM(L: var TBaseLexer) =
if L.buf[0] == '\xEF' and L.buf[1] == '\xBB' and L.buf[2] == '\xBF':
inc(L.bufpos, 3)
inc(L.lineStart, 3)
proc openBaseLexer(L: var TBaseLexer, inputstream: PLLStream, bufLen = 8192) =
assert(bufLen > 0)
L.bufpos = 0
L.offsetBase = 0
L.buf = newString(bufLen)
L.sentinel = bufLen - 1
L.lineStart = 0
L.lineNumber = 1 # lines start at 1
L.stream = inputstream
fillBuffer(L)
skipUTF8BOM(L)
proc getColNumber(L: TBaseLexer, pos: int): int =
result = abs(pos - L.lineStart)
proc getCurrentLine(L: TBaseLexer, marker: bool = true): string =
result = ""
var i = L.lineStart
while not (L.buf[i] in {CR, LF, EndOfFile}):
add(result, L.buf[i])
inc(i)
result.add("\n")
if marker:
result.add(spaces(getColNumber(L, L.bufpos)) & '^' & "\n")
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