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6c52614864
It is useful to be able to rewind a check-summed file to a certain previous state after writing data into it using sha1write() API. The fast-import command does this after streaming a blob data to the packfile being generated and then noticing that the same blob has already been written, and it does this with a private code truncate_pack() that is commented as "Yes, this is a layering violation". Introduce two API functions, sha1file_checkpoint(), that allows the caller to save a state of a sha1file, and then later revert it to the saved state. Use it to reimplement truncate_pack(). Signed-off-by: Junio C Hamano <gitster@pobox.com>
192 lines
4.0 KiB
C
192 lines
4.0 KiB
C
/*
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* csum-file.c
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*
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* Copyright (C) 2005 Linus Torvalds
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*
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* Simple file write infrastructure for writing SHA1-summed
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* files. Useful when you write a file that you want to be
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* able to verify hasn't been messed with afterwards.
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*/
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#include "cache.h"
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#include "progress.h"
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#include "csum-file.h"
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static void flush(struct sha1file *f, void *buf, unsigned int count)
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{
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if (0 <= f->check_fd && count) {
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unsigned char check_buffer[8192];
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ssize_t ret = read_in_full(f->check_fd, check_buffer, count);
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if (ret < 0)
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die_errno("%s: sha1 file read error", f->name);
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if (ret < count)
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die("%s: sha1 file truncated", f->name);
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if (memcmp(buf, check_buffer, count))
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die("sha1 file '%s' validation error", f->name);
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}
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for (;;) {
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int ret = xwrite(f->fd, buf, count);
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if (ret > 0) {
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f->total += ret;
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display_throughput(f->tp, f->total);
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buf = (char *) buf + ret;
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count -= ret;
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if (count)
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continue;
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return;
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}
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if (!ret)
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die("sha1 file '%s' write error. Out of diskspace", f->name);
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die_errno("sha1 file '%s' write error", f->name);
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}
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}
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void sha1flush(struct sha1file *f)
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{
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unsigned offset = f->offset;
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if (offset) {
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git_SHA1_Update(&f->ctx, f->buffer, offset);
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flush(f, f->buffer, offset);
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f->offset = 0;
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}
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}
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int sha1close(struct sha1file *f, unsigned char *result, unsigned int flags)
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{
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int fd;
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sha1flush(f);
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git_SHA1_Final(f->buffer, &f->ctx);
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if (result)
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hashcpy(result, f->buffer);
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if (flags & (CSUM_CLOSE | CSUM_FSYNC)) {
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/* write checksum and close fd */
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flush(f, f->buffer, 20);
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if (flags & CSUM_FSYNC)
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fsync_or_die(f->fd, f->name);
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if (close(f->fd))
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die_errno("%s: sha1 file error on close", f->name);
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fd = 0;
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} else
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fd = f->fd;
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if (0 <= f->check_fd) {
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char discard;
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int cnt = read_in_full(f->check_fd, &discard, 1);
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if (cnt < 0)
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die_errno("%s: error when reading the tail of sha1 file",
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f->name);
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if (cnt)
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die("%s: sha1 file has trailing garbage", f->name);
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if (close(f->check_fd))
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die_errno("%s: sha1 file error on close", f->name);
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}
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free(f);
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return fd;
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}
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int sha1write(struct sha1file *f, void *buf, unsigned int count)
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{
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while (count) {
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unsigned offset = f->offset;
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unsigned left = sizeof(f->buffer) - offset;
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unsigned nr = count > left ? left : count;
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void *data;
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if (f->do_crc)
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f->crc32 = crc32(f->crc32, buf, nr);
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if (nr == sizeof(f->buffer)) {
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/* process full buffer directly without copy */
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data = buf;
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} else {
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memcpy(f->buffer + offset, buf, nr);
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data = f->buffer;
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}
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count -= nr;
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offset += nr;
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buf = (char *) buf + nr;
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left -= nr;
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if (!left) {
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git_SHA1_Update(&f->ctx, data, offset);
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flush(f, data, offset);
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offset = 0;
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}
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f->offset = offset;
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}
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return 0;
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}
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struct sha1file *sha1fd(int fd, const char *name)
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{
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return sha1fd_throughput(fd, name, NULL);
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}
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struct sha1file *sha1fd_check(const char *name)
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{
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int sink, check;
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struct sha1file *f;
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sink = open("/dev/null", O_WRONLY);
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if (sink < 0)
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return NULL;
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check = open(name, O_RDONLY);
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if (check < 0) {
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int saved_errno = errno;
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close(sink);
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errno = saved_errno;
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return NULL;
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}
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f = sha1fd(sink, name);
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f->check_fd = check;
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return f;
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}
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struct sha1file *sha1fd_throughput(int fd, const char *name, struct progress *tp)
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{
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struct sha1file *f = xmalloc(sizeof(*f));
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f->fd = fd;
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f->check_fd = -1;
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f->offset = 0;
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f->total = 0;
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f->tp = tp;
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f->name = name;
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f->do_crc = 0;
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git_SHA1_Init(&f->ctx);
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return f;
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}
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void sha1file_checkpoint(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
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{
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sha1flush(f);
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checkpoint->offset = f->total;
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checkpoint->ctx = f->ctx;
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}
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int sha1file_truncate(struct sha1file *f, struct sha1file_checkpoint *checkpoint)
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{
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off_t offset = checkpoint->offset;
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if (ftruncate(f->fd, offset) ||
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lseek(f->fd, offset, SEEK_SET) != offset)
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return -1;
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f->total = offset;
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f->ctx = checkpoint->ctx;
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f->offset = 0; /* sha1flush() was called in checkpoint */
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return 0;
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}
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void crc32_begin(struct sha1file *f)
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{
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f->crc32 = crc32(0, NULL, 0);
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f->do_crc = 1;
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}
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uint32_t crc32_end(struct sha1file *f)
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{
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f->do_crc = 0;
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return f->crc32;
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}
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