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#include "parse.h"
static const size_t max_ssize_t = (((size_t)1) << (sizeof(size_t)*8-1))-1;
/* Read n bytes from stream. Return n.
* Set stream to error state if not enough space or I/O error. */
ssize_t prs_readblob(struct bytestream* bs,unsigned char* dest,size_t destlen) {
ssize_t r;
if (destlen > max_ssize_t)
destlen = max_ssize_t;
if (!bs_capacityassert(bs,destlen)) return -1;
r = destlen;
switch (bs->type) {
case MEMBUF:
memcpy(dest, bs->u.base+bs->cur, destlen);
bs->cur += destlen;
break;
case IOBUF:
buffer_get(bs->u.b, (char*)dest, destlen);
break;
case BSTREAM:
bs->cur += destlen;
r=prs_readblob(bs->u.bs, dest, destlen);
if (r != (ssize_t)destlen) {
bs->cur = 1; // set bytestream to error state
bs->max = 0;
return -1;
}
break;
}
return r;
}
#ifdef UNITTEST
#include <assert.h>
#undef UNITTEST
#include "buffer/bs_get.c"
#include "buffer/bs_err.c"
#include "buffer/bs_capacityassert.c"
#include "buffer/bs_init_iobuf_size.c"
#include "buffer/bs_init_membuf.c"
#include "buffer/buffer_get.c"
#include "buffer/buffer_getc.c"
#include "buffer/buffer_feed.c"
#include "buffer/buffer_stubborn2.c"
#include "byte/byte_copy.c"
#include "open/open_read.c"
int main() {
struct bytestream bs = BS_FROM_MEMBUF("\x34\x12", 2);
char buf[42];
assert(prs_readblob(&bs, buf, 2) == 2);
assert(bs_err(&bs) == 0);
assert(!memcmp(buf,"\x34\x12",2));
assert(prs_readblob(&bs, buf, 1) == -1);
assert(bs_err(&bs));
// now try to provoke integer overflow
bs_init_membuf(&bs, "\x34\x12", 2);
assert(bs_get(&bs) == 0x34);
assert(prs_readblob(&bs, buf, (size_t)-1) == -1);
// a bad implementation would add 0xffffffff to the 1 we already read and wrap to 0
// our code makes sure not to wrap and also limits the length of the
// blob to max_ssize_t (0x7fffffff).
assert(bs_err(&bs));
int fd = open_read("Makefile");
assert(fd!=-1);
buffer b = BUFFER_INIT(read, fd, buf+32, 10);
bs_init_iobuf_size(&bs, &b, 100);
assert(prs_readblob(&bs, buf, 20) == 20); // make sure we can read a 20 byte blob at once even if the iobuf buffer size is smaller
// strace will show two read calls here
}
#endif