root/csum-file.c

DEFINITIONS

1. flush
2. sha1flush
3. sha1close
4. sha1write
5. sha1fd
6. sha1fd_check
7. sha1fd_throughput
8. sha1file_checkpoint
9. sha1file_truncate
10. crc32_begin
11. crc32_end

/*
 * 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)
                die_errno("unable to open /dev/null");
        check = open(name, O_RDONLY);
        if (check < 0)
                die_errno("unable to open '%s'", name);
        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;
}