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#include "system.h"
#include <errno.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/mman.h>
int
crc32_file (int fd, uint32_t *resp)
{
unsigned char buffer[1024 * 8];
uint32_t crc = 0;
off_t off = 0;
ssize_t count;
struct stat st;
if (fstat (fd, &st) == 0)
{
/* Try mapping in the file data. */
size_t mapsize = st.st_size;
void *mapped = mmap (NULL, mapsize, PROT_READ, MAP_PRIVATE, fd, 0);
if (mapped == MAP_FAILED && errno == ENOMEM)
{
const size_t pagesize = sysconf (_SC_PAGE_SIZE);
mapsize = ((mapsize / 2) + pagesize - 1) & -pagesize;
while (mapsize >= pagesize
&& (mapped = mmap (NULL, mapsize, PROT_READ, MAP_PRIVATE,
fd, 0)) == MAP_FAILED && errno == ENOMEM)
mapsize /= 2;
}
if (mapped != MAP_FAILED)
{
do
{
if (st.st_size <= (off_t) mapsize)
{
*resp = crc32 (crc, mapped, st.st_size);
munmap (mapped, mapsize);
return 0;
}
crc = crc32 (crc, mapped, mapsize);
off += mapsize;
st.st_size -= mapsize;
} while (mmap (mapped, mapsize, PROT_READ, MAP_FIXED|MAP_PRIVATE,
fd, off) == mapped);
munmap (mapped, mapsize);
}
}
while ((count = TEMP_FAILURE_RETRY (pread (fd, buffer, sizeof buffer,
off))) > 0)
{
off += count;
crc = crc32 (crc, buffer, count);
}
*resp = crc;
return count == 0 ? 0 : -1;
}
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