git/csum-file.c
brian m. carlson 768e30ea27 hash: implement and use a context cloning function
For all of our SHA-1 implementations and most of our SHA-256
implementations, the hash context we use is a real struct.  For these
implementations, it's possible to copy a hash context by making a copy
of the struct.

However, for our libgcrypt implementation, our hash context is a
pointer.  Consequently, copying it does not lead to an independent hash
context like we intended.

Fortunately, however, libgcrypt provides us with a handy function to
copy hash contexts.  Let's add a cloning function to the hash algorithm
API, and use it in the one place we need to make a hash context copy.
With this change, our libgcrypt SHA-256 implementation is fully
functional with all of our other hash implementations.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-02-24 09:33:21 -08:00

187 lines
4.1 KiB
C

/*
* csum-file.c
*
* Copyright (C) 2005 Linus Torvalds
*
* Simple file write infrastructure for writing SHA1-summed
* files. Useful when you write a file that you want to be
* able to verify hasn't been messed with afterwards.
*/
#include "cache.h"
#include "progress.h"
#include "csum-file.h"
static void flush(struct hashfile *f, const void *buf, unsigned int count)
{
if (0 <= f->check_fd && count) {
unsigned char check_buffer[8192];
ssize_t ret = read_in_full(f->check_fd, check_buffer, count);
if (ret < 0)
die_errno("%s: sha1 file read error", f->name);
if (ret != count)
die("%s: sha1 file truncated", f->name);
if (memcmp(buf, check_buffer, count))
die("sha1 file '%s' validation error", f->name);
}
for (;;) {
int ret = xwrite(f->fd, buf, count);
if (ret > 0) {
f->total += ret;
display_throughput(f->tp, f->total);
buf = (char *) buf + ret;
count -= ret;
if (count)
continue;
return;
}
if (!ret)
die("sha1 file '%s' write error. Out of diskspace", f->name);
die_errno("sha1 file '%s' write error", f->name);
}
}
void hashflush(struct hashfile *f)
{
unsigned offset = f->offset;
if (offset) {
the_hash_algo->update_fn(&f->ctx, f->buffer, offset);
flush(f, f->buffer, offset);
f->offset = 0;
}
}
int finalize_hashfile(struct hashfile *f, unsigned char *result, unsigned int flags)
{
int fd;
hashflush(f);
the_hash_algo->final_fn(f->buffer, &f->ctx);
if (result)
hashcpy(result, f->buffer);
if (flags & CSUM_HASH_IN_STREAM)
flush(f, f->buffer, the_hash_algo->rawsz);
if (flags & CSUM_FSYNC)
fsync_or_die(f->fd, f->name);
if (flags & CSUM_CLOSE) {
if (close(f->fd))
die_errno("%s: sha1 file error on close", f->name);
fd = 0;
} else
fd = f->fd;
if (0 <= f->check_fd) {
char discard;
int cnt = read_in_full(f->check_fd, &discard, 1);
if (cnt < 0)
die_errno("%s: error when reading the tail of sha1 file",
f->name);
if (cnt)
die("%s: sha1 file has trailing garbage", f->name);
if (close(f->check_fd))
die_errno("%s: sha1 file error on close", f->name);
}
free(f);
return fd;
}
void hashwrite(struct hashfile *f, const void *buf, unsigned int count)
{
while (count) {
unsigned offset = f->offset;
unsigned left = sizeof(f->buffer) - offset;
unsigned nr = count > left ? left : count;
const void *data;
if (f->do_crc)
f->crc32 = crc32(f->crc32, buf, nr);
if (nr == sizeof(f->buffer)) {
/* process full buffer directly without copy */
data = buf;
} else {
memcpy(f->buffer + offset, buf, nr);
data = f->buffer;
}
count -= nr;
offset += nr;
buf = (char *) buf + nr;
left -= nr;
if (!left) {
the_hash_algo->update_fn(&f->ctx, data, offset);
flush(f, data, offset);
offset = 0;
}
f->offset = offset;
}
}
struct hashfile *hashfd(int fd, const char *name)
{
return hashfd_throughput(fd, name, NULL);
}
struct hashfile *hashfd_check(const char *name)
{
int sink, check;
struct hashfile *f;
sink = open("/dev/null", O_WRONLY);
if (sink < 0)
die_errno("unable to open /dev/null");
check = open(name, O_RDONLY);
if (check < 0)
die_errno("unable to open '%s'", name);
f = hashfd(sink, name);
f->check_fd = check;
return f;
}
struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp)
{
struct hashfile *f = xmalloc(sizeof(*f));
f->fd = fd;
f->check_fd = -1;
f->offset = 0;
f->total = 0;
f->tp = tp;
f->name = name;
f->do_crc = 0;
the_hash_algo->init_fn(&f->ctx);
return f;
}
void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
{
hashflush(f);
checkpoint->offset = f->total;
the_hash_algo->clone_fn(&checkpoint->ctx, &f->ctx);
}
int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
{
off_t offset = checkpoint->offset;
if (ftruncate(f->fd, offset) ||
lseek(f->fd, offset, SEEK_SET) != offset)
return -1;
f->total = offset;
f->ctx = checkpoint->ctx;
f->offset = 0; /* hashflush() was called in checkpoint */
return 0;
}
void crc32_begin(struct hashfile *f)
{
f->crc32 = crc32(0, NULL, 0);
f->do_crc = 1;
}
uint32_t crc32_end(struct hashfile *f)
{
f->do_crc = 0;
return f->crc32;
}