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#include "parse.h"
static const size_t max_ssize_t = (((size_t)1) << (sizeof(size_t)*8-1))-1;
/* Read an asciiz string from the byte stream, up to len bytes (including the 0 terminator). */
/* Return number of bytes consumed (excluding the 0 terminator), i.e. strlen(dest) */
/* If there is no 0 byte in these len bytes, set error flag in stream and return -1. */
/* Calling this function with len==0 is an error. */
/* destsize will be clamped to the maximum number representable in ssize_t */
ssize_t prs_asciiz(struct bytestream* bs, char* dest, size_t len) {
size_t i;
/* The maximum value of ssize_t is half that of size_t.
* So we arbitrarily decide to limit len to it here. */
if (len>max_ssize_t) len=max_ssize_t;
if (len==0) {
bs->cur = 1; // mark bytestream state as erroneous
bs->max = 0;
return -1;
}
for (i=0; i+1<len; ++i)
if ((dest[i] = bs_get(bs)) == 0) {
/* we might get here either because there actually was a 0 byte in
* the stream, or because we hit EOF. So check if we hit EOF here
* and return -1 then. */
return (bs->cur<=bs->max) ? (ssize_t)i : -1;
}
/* if we get here, we read len-1 bytes and there was no 0 byte. */
if ((dest[i] = bs_peek(bs))) { // the loop went till i+1<len and we checked that len!=0
// the next byte was not 0, so signal error
bs->cur = 1;
bs->max = 0;
// but still write 0 terminator to dest
dest[i] = 0;
return -1;
} else {
bs_get(bs); // the next byte was 0, so consume it
return i;
}
}
#ifdef UNITTEST
#include <assert.h>
#undef UNITTEST
#include "buffer/bs_init_membuf.c"
#include "buffer/bs_get.c"
#include "buffer/bs_err.c"
#include "buffer/bs_peek.c"
// we use membuf here, mock buffer stuff away
ssize_t buffer_getc(buffer* b,char* x) { return 0; }
ssize_t buffer_peekc(buffer* b,char* x) { return 0; }
int main() {
struct bytestream bs = BS_FROM_MEMBUF("fnord\n\0x",8);
char buf[100];
assert(prs_asciiz(&bs, buf, sizeof buf) == 6); // return value should be strlen("fnord\n")
assert(!memcmp(buf,"fnord\n",7)); // returned string should be "fnord\n" with 0 terminator
assert(bs_get(&bs) == 'x'); // should have consumed the 0 terminator from bytestream
bs_init_membuf(&bs, (const unsigned char*)"fnord\n\0x", 8);
assert(prs_asciiz(&bs, buf, 5) == -1); // no 0 terminator in first 5 bytes, expect error
assert(!memcmp(buf,"fnor",5)); // expect 4 bytes + 0 terminator in dest buf
assert(bs_err(&bs)); // bytestream should be in error state now
}
#endif