[PATCH] Operations on refs
[git/git.git] / refs.c
1 #include "refs.h"
2 #include "cache.h"
3
4 #include <errno.h>
5
6 static char *ref_file_name(const char *ref)
7 {
8 char *base = get_refs_directory();
9 int baselen = strlen(base);
10 int reflen = strlen(ref);
11 char *ret = xmalloc(baselen + 2 + reflen);
12 sprintf(ret, "%s/%s", base, ref);
13 return ret;
14 }
15
16 static char *ref_lock_file_name(const char *ref)
17 {
18 char *base = get_refs_directory();
19 int baselen = strlen(base);
20 int reflen = strlen(ref);
21 char *ret = xmalloc(baselen + 7 + reflen);
22 sprintf(ret, "%s/%s.lock", base, ref);
23 return ret;
24 }
25
26 static int read_ref_file(const char *filename, unsigned char *sha1) {
27 int fd = open(filename, O_RDONLY);
28 char hex[41];
29 if (fd < 0) {
30 return error("Couldn't open %s\n", filename);
31 }
32 if ((read(fd, hex, 41) < 41) ||
33 (hex[40] != '\n') ||
34 get_sha1_hex(hex, sha1)) {
35 error("Couldn't read a hash from %s\n", filename);
36 close(fd);
37 return -1;
38 }
39 close(fd);
40 return 0;
41 }
42
43 int get_ref_sha1(const char *ref, unsigned char *sha1)
44 {
45 char *filename;
46 int retval;
47 if (check_ref_format(ref))
48 return -1;
49 filename = ref_file_name(ref);
50 retval = read_ref_file(filename, sha1);
51 free(filename);
52 return retval;
53 }
54
55 static int lock_ref_file(const char *filename, const char *lock_filename,
56 const unsigned char *old_sha1)
57 {
58 int fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
59 unsigned char current_sha1[20];
60 int retval;
61 if (fd < 0) {
62 return error("Couldn't open lock file for %s: %s",
63 filename, strerror(errno));
64 }
65 retval = read_ref_file(filename, current_sha1);
66 if (old_sha1) {
67 if (retval) {
68 close(fd);
69 unlink(lock_filename);
70 return error("Could not read the current value of %s",
71 filename);
72 }
73 if (memcmp(current_sha1, old_sha1, 20)) {
74 close(fd);
75 unlink(lock_filename);
76 error("The current value of %s is %s",
77 filename, sha1_to_hex(current_sha1));
78 return error("Expected %s",
79 sha1_to_hex(old_sha1));
80 }
81 } else {
82 if (!retval) {
83 close(fd);
84 unlink(lock_filename);
85 return error("Unexpectedly found a value of %s for %s",
86 sha1_to_hex(current_sha1), filename);
87 }
88 }
89 return fd;
90 }
91
92 int lock_ref_sha1(const char *ref, const unsigned char *old_sha1)
93 {
94 char *filename;
95 char *lock_filename;
96 int retval;
97 if (check_ref_format(ref))
98 return -1;
99 filename = ref_file_name(ref);
100 lock_filename = ref_lock_file_name(ref);
101 retval = lock_ref_file(filename, lock_filename, old_sha1);
102 free(filename);
103 free(lock_filename);
104 return retval;
105 }
106
107 static int write_ref_file(const char *filename,
108 const char *lock_filename, int fd,
109 const unsigned char *sha1)
110 {
111 char *hex = sha1_to_hex(sha1);
112 char term = '\n';
113 if (write(fd, hex, 40) < 40 ||
114 write(fd, &term, 1) < 1) {
115 error("Couldn't write %s\n", filename);
116 close(fd);
117 return -1;
118 }
119 close(fd);
120 rename(lock_filename, filename);
121 return 0;
122 }
123
124 int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
125 {
126 char *filename;
127 char *lock_filename;
128 int retval;
129 if (fd < 0)
130 return -1;
131 if (check_ref_format(ref))
132 return -1;
133 filename = ref_file_name(ref);
134 lock_filename = ref_lock_file_name(ref);
135 retval = write_ref_file(filename, lock_filename, fd, sha1);
136 free(filename);
137 free(lock_filename);
138 return retval;
139 }
140
141 int check_ref_format(const char *ref)
142 {
143 char *middle;
144 if (ref[0] == '.' || ref[0] == '/')
145 return -1;
146 middle = strchr(ref, '/');
147 if (!middle || !middle[1])
148 return -1;
149 if (strchr(middle + 1, '/'))
150 return -1;
151 return 0;
152 }
153
154 int write_ref_sha1_unlocked(const char *ref, const unsigned char *sha1)
155 {
156 char *filename;
157 char *lock_filename;
158 int fd;
159 int retval;
160 if (check_ref_format(ref))
161 return -1;
162 filename = ref_file_name(ref);
163 lock_filename = ref_lock_file_name(ref);
164 fd = open(lock_filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
165 if (fd < 0) {
166 error("Writing %s", lock_filename);
167 perror("Open");
168 }
169 retval = write_ref_file(filename, lock_filename, fd, sha1);
170 free(filename);
171 free(lock_filename);
172 return retval;
173 }