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#include "parse.h"
static const size_t max_ssize_t = (((size_t)1) << (sizeof(size_t)*8-1))-1;
/* Some protocols have a fixed field length for a string,
* If the string is shorter than the field, the rest is filled with 0
* bytes. But it is not an error if there are no 0 bytes.
* This function is for those cases (the filename field in the tar file
* header is an example of this).
* For a field of length 8, you need to pass destsize as 9 so we can add
* a 0 terminator. This function will consume the 8 bytes and add a 0 byte.
* The return value is strlen(dest). */
ssize_t prs_asciiz_fixedlen(struct bytestream* bs, char* dest, size_t len) {
size_t i;
ssize_t r=0;
/* 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 && r==0)
r=i; // note the position of the first 0 byte
dest[i] = 0; // add 0 terminator
if (dest[r]) r=i;
return bs_err(bs) ? -1 : r;
}
#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_fixedlen(&bs, buf, 8) == 6); // return value should be strlen("fnord\n")
assert(!memcmp(buf,"fnord\n\0\0",8)); // returned string should be "fnord\n" and the rest filled with 0 bytes
assert(!bs_err(&bs));
bs_init_membuf(&bs, (const unsigned char*)"fnord\n\0x", 8);
assert(prs_asciiz_fixedlen(&bs, buf, 5) == 4); // no 0 terminator in first 4 bytes
assert(!memcmp(buf,"fnor",5)); // expect 4 bytes + 0 terminator in dest buf
assert(bs_get(&bs) == 'd'); // 0 terminator in buf was artificial, 'd' was not consumed
assert(!bs_err(&bs)); // bytestream should be ok
}
#endif