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#
#
# The Nimrod 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 TObject
bufpos*: int
buf*: cstring
bufLen*: int # length of buffer in characters
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
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
const
chrSize = sizeof(char)
proc closeBaseLexer(L: var TBaseLexer) =
dealloc(L.buf)
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.bufLen)
toCopy = L.BufLen - L.sentinel - 1
assert(toCopy >= 0)
if toCopy > 0:
MoveMem(L.buf, addr(L.buf[L.sentinel + 1]), toCopy * chrSize)
# "moveMem" handles overlapping regions
charsRead = LLStreamRead(L.stream, addr(L.buf[toCopy]),
(L.sentinel + 1) * chrSize) div chrSize
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.bufLen)
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.BufLen
L.bufLen = L.BufLen * 2
L.buf = cast[cstring](realloc(L.buf, L.bufLen * chrSize))
assert(L.bufLen - oldBuflen == oldBufLen)
charsRead = LLStreamRead(L.stream, addr(L.buf[oldBufLen]),
oldBufLen * chrSize) div chrSize
if charsRead < oldBufLen:
L.buf[oldBufLen + charsRead] = EndOfFile
L.sentinel = oldBufLen + charsRead
break
s = L.bufLen - 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.bufpos = 0 # XXX: is this really correct?
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.bufLen = bufLen
L.buf = cast[cstring](alloc(bufLen * chrSize))
L.sentinel = bufLen - 1
L.lineStart = 0
L.linenumber = 1 # lines start at 1
L.stream = inputstream
fillBuffer(L)
skip_UTF_8_BOM(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(RepeatChar(getColNumber(L, L.bufpos)) & '^' & "\n")
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