gitソース解析(四)commit-tree

commit-treeコマンドは、後のgit commitコマンド、フォーマットcommit-tree[-p]に似ています.

int main(int argc, char **argv)
{
    unsigned char tree_sha1[20];
    get_sha1_hex(argv[1], tree_sha1);
    for (i = 2; i < argc; i += 2)
        a = argv[i]; b = argv[i+1];
        if (!b || strcmp(a, "-p") || get_sha1_hex(b, parent_sha1[parents]))
            usage("commit-tree  [-p ]* < changelog");
        parents++;
    init_buffer(&buffer, &size);
    add_buffer(&buffer, &size, "tree %s
", sha1_to_hex(tree_sha1));
    for (i = 0; i < parents; i++)
        add_buffer(&buffer, &size, "parent %s
", sha1_to_hex(parent_sha1[i]));
    add_buffer(&buffer, &size, "author %s  %s
", gecos, email, date);
    add_buffer(&buffer, &size, "committer %s  %s

", realgecos, realemail, realdate);
    while (fgets(comment, sizeof(comment), stdin) != NULL)
        add_buffer(&buffer, &size, "%s", comment);
    finish_buffer("commit ", &buffer, &size); 
    // buffer: "commit %lu\0tree %s
parent %s
..parent %s
author %s  %s
committer %s  %s

%s"
    // %lu: size of "tree %s
parent %s
..parent %s
author %s  %s
committer %s  %s

%s"
    // size: size of buffer
    write_sha1_file(buffer, size);
        stream.next_in = buffer;
        stream.avail_in = size;
        stream.next_out = compressed;
        stream.avail_out = len;
        while (deflate(&stream, Z_FINISH) == Z_OK);
        size = stream.total_out;
        SHA1_Init(&c);
        SHA1_Update(&c, compressed, size);
        SHA1_Final(sha1, &c);
        write_sha1_buffer(sha1, compressed, size);
            char *filename = sha1_file_name(sha1);
            fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
            write(fd, compressed, size);
            close(fd);
}

 
1.buffer情報フォーマット:commit%lu0 tree%sparent%sauthor%s%scommitter%s%s%s%s
%lu#「tree%sparent%sauthor%s%scommitter%s%s%s」コンテンツ長
 
2. write_sha1_file(buffer, size); # sha 1ファイルに情報を書き込む

int write_sha1_file(char *buf, unsigned len)
{
	int size;
	char *compressed;
	z_stream stream;
	unsigned char sha1[20];
	SHA_CTX c;

	/* Set it up */
	memset(&stream, 0, sizeof(stream));
	deflateInit(&stream, Z_BEST_COMPRESSION);
	size = deflateBound(&stream, len);
	compressed = malloc(size);

	/* Compress it */
	stream.next_in = buf;
	stream.avail_in = len;
	stream.next_out = compressed;
	stream.avail_out = size;
	while (deflate(&stream, Z_FINISH) == Z_OK)
		/* nothing */;
	deflateEnd(&stream);
	size = stream.total_out;

	/* Sha1.. */
	SHA1_Init(&c);
	SHA1_Update(&c, compressed, size);
	SHA1_Final(sha1, &c);

	if (write_sha1_buffer(sha1, compressed, size) < 0)
		return -1;
	printf("%s
", sha1_to_hex(sha1));
	return 0;
}

2.1 write_sha1_buffer(sha1, compressed, size); # 組み立てたbuffer情報を圧縮し、圧縮値にhashを取り、sha 1ファイルに圧縮内容を書き込む

int write_sha1_buffer(unsigned char *sha1, void *buf, unsigned int size)
{
	char *filename = sha1_file_name(sha1);
	int i, fd;

	fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
	if (fd < 0)
		return (errno == EEXIST) ? 0 : -1;
	write(fd, buf, size);
	close(fd);
	return 0;
}

2.1.1 char *filename = sha1_file_name(sha1); # hash値から生成する.dircache/objects/xx/xx..xx(38ビット)ファイル名
2.1.2新規作成およびsha 1ファイルへの圧縮データの書き込み