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/*
* 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 sha1file *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 sha1flush(struct sha1file *f)
{
unsigned offset = f->offset;

if (offset) {
git_SHA1_Update(&f->ctx, f->buffer, offset);
flush(f, f->buffer, offset);
f->offset = 0;
}
}

int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
{
int fd;

sha1flush(f);
git_SHA1_Final(f->buffer, &f->ctx);
if (result)
hashcpy(result, f->buffer);
if (flags & (CSUM_CLOSE | CSUM_FSYNC)) {
/* write checksum and close fd */
flush(f, f->buffer, 20);
if (flags & CSUM_FSYNC)
fsync_or_die(f->fd, f->name);
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 sha1write(struct sha1file *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) {
git_SHA1_Update(&f->ctx, data, offset);
flush(f, data, offset);
offset = 0;
}
f->offset = offset;
}
}

struct sha1file *sha1fd(int fd, const char *name)
{
return sha1fd_throughput(fd, name, NULL);
}

struct sha1file *sha1fd_check(const char *name)
{
int sink, check;
struct sha1file *f;

sink = open("/dev/null", O_WRONLY);
if (sink < 0)
return NULL;
check = open(name, O_RDONLY);
if (check < 0) {
int saved_errno = errno;
close(sink);
errno = saved_errno;
return NULL;
}
f = sha1fd(sink, name);
f->check_fd = check;
return f;
}

struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp)
{
struct sha1file *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;
git_SHA1_Init(&f->ctx);
return f;
}

void sha1file_checkpoint(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
{
sha1flush(f);
checkpoint->offset = f->total;
checkpoint->ctx = f->ctx;
}

int sha1file_truncate(struct sha1file *f, struct sha1file_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; /* sha1flush() was called in checkpoint */
return 0;
}

void crc32_begin(struct sha1file *f)
{
f->crc32 = crc32(0, NULL, 0);
f->do_crc = 1;
}

uint32_t crc32_end(struct sha1file *f)
{
f->do_crc = 0;
return f->crc32;
}
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