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Turn the readChars macro into a readInternal function

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This macro was only used twice, and the second usage did
some unnecessary work.
This commit is contained in:
Rangi
2021-11-24 17:18:35 -05:00
committed by Eldred Habert
parent b7fe78cad8
commit 8435a29c4e
1 changed files with 24 additions and 22 deletions
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46
src/asm/lexer.c
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@@ -808,6 +808,19 @@ static char const *readMacroArg(char name)
return str;
}
static size_t readInternal(size_t bufIndex, size_t nbChars)
{
// This buffer overflow made me lose WEEKS of my life. Never again.
assert(bufIndex + nbChars <= LEXER_BUF_SIZE);
ssize_t nbReadChars = read(lexerState->fd, &lexerState->buf[bufIndex], nbChars);
if (nbReadChars == -1)
fatalerror("Error while reading \"%s\": %s\n", lexerState->path, strerror(errno));
// `nbReadChars` cannot be negative, so it's fine to cast to `size_t`
return (size_t)nbReadChars;
}
/* We only need one character of lookahead, for macro arguments */
static int peekInternal(uint8_t distance)
{
@@ -839,42 +852,31 @@ static int peekInternal(uint8_t distance)
/* Compute the index we'll start writing to */
size_t writeIndex = (lexerState->index + lexerState->nbChars) % LEXER_BUF_SIZE;
ssize_t nbCharsRead = 0, totalCharsRead = 0;
#define readChars(size) do { \
/* This buffer overflow made me lose WEEKS of my life. Never again. */ \
assert(writeIndex + (size) <= LEXER_BUF_SIZE); \
nbCharsRead = read(lexerState->fd, &lexerState->buf[writeIndex], (size)); \
if (nbCharsRead == -1) \
fatalerror("Error while reading \"%s\": %s\n", lexerState->path, strerror(errno)); \
totalCharsRead += nbCharsRead; \
writeIndex += nbCharsRead; \
if (writeIndex == LEXER_BUF_SIZE) \
writeIndex = 0; \
target -= nbCharsRead; \
} while (0)
/* If the range to fill passes over the buffer wrapping point, we need two reads */
if (writeIndex + target > LEXER_BUF_SIZE) {
size_t nbExpectedChars = LEXER_BUF_SIZE - writeIndex;
size_t nbReadChars = readInternal(writeIndex, nbExpectedChars);
lexerState->nbChars += nbReadChars;
writeIndex += nbReadChars;
if (writeIndex == LEXER_BUF_SIZE)
writeIndex = 0;
readChars(nbExpectedChars);
// If the read was incomplete, don't perform a second read
// `nbCharsRead` cannot be negative, so it's fine to cast to `size_t`
if ((size_t)nbCharsRead < nbExpectedChars)
target -= nbReadChars;
if (nbReadChars < nbExpectedChars)
target = 0;
}
if (target != 0)
readChars(target);
#undef readChars
lexerState->nbChars += totalCharsRead;
lexerState->nbChars += readInternal(writeIndex, target);
/* If there aren't enough chars even after refilling, give up */
if (lexerState->nbChars <= distance)
return EOF;
}
return (unsigned char)lexerState->buf[(lexerState->index + distance) % LEXER_BUF_SIZE];
}