1/*
2 * Copyright (C) 2008 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include <ctype.h>
18#include <errno.h>
19#include <getopt.h>
20#include <limits.h>
21#include <stdio.h>
22#include <stdlib.h>
23#include <string.h>
24
25/*
26 * Append a tag to a property value in a .prop file if it isn't already there.
27 * Normally used to modify build properties to record incremental updates.
28 */
29
30// Return nonzero if the tag should be added to this line.
31int should_tag(const char *line, const char *propname) {
32    const char *prop = strstr(line, propname);
33    if (prop == NULL) return 0;
34
35    // Make sure this is actually the property name (not an accidental hit)
36    const char *ptr;
37    for (ptr = line; ptr < prop && isspace(*ptr); ++ptr) ;
38    if (ptr != prop) return 0;  // Must be at the beginning of the line
39
40    for (ptr += strlen(propname); *ptr != '\0' && isspace(*ptr); ++ptr) ;
41    return (*ptr == '=');  // Must be followed by a '='
42}
43
44// Remove existing tags from the line, return the following number (if any)
45int remove_tag(char *line, const char *tag) {
46    char *pos = strstr(line, tag);
47    if (pos == NULL) return 0;
48
49    char *end;
50    int num = strtoul(pos + strlen(tag), &end, 10);
51    strcpy(pos, end);
52    return num;
53}
54
55// Write line to output with the tag added, adding a number (if >0)
56void write_tagged(FILE *out, const char *line, const char *tag, int number) {
57    const char *end = line + strlen(line);
58    while (end > line && isspace(end[-1])) --end;
59    if (number > 0) {
60        fprintf(out, "%.*s%s%d%s", (int)(end - line), line, tag, number, end);
61    } else {
62        fprintf(out, "%.*s%s%s", (int)(end - line), line, tag, end);
63    }
64}
65
66int main(int argc, char **argv) {
67    const char *filename = "/system/build.prop";
68    const char *propname = "ro.build.fingerprint";
69    const char *tag = NULL;
70    int do_remove = 0, do_number = 0;
71
72    int opt;
73    while ((opt = getopt(argc, argv, "f:p:rn")) != -1) {
74        switch (opt) {
75        case 'f': filename = optarg; break;
76        case 'p': propname = optarg; break;
77        case 'r': do_remove = 1; break;
78        case 'n': do_number = 1; break;
79        case '?': return 2;
80        }
81    }
82
83    if (argc != optind + 1) {
84        fprintf(stderr,
85            "usage: add-property-tag [flags] tag-to-add\n"
86            "flags: -f /dir/file.prop (default /system/build.prop)\n"
87            "       -p prop.name (default ro.build.fingerprint)\n"
88            "       -r (if set, remove the tag rather than adding it)\n"
89            "       -n (if set, add and increment a number after the tag)\n");
90        return 2;
91    }
92
93    tag = argv[optind];
94    FILE *input = fopen(filename, "r");
95    if (input == NULL) {
96        fprintf(stderr, "can't read %s: %s\n", filename, strerror(errno));
97        return 1;
98    }
99
100    char tmpname[PATH_MAX];
101    snprintf(tmpname, sizeof(tmpname), "%s.tmp", filename);
102    FILE *output = fopen(tmpname, "w");
103    if (output == NULL) {
104        fprintf(stderr, "can't write %s: %s\n", tmpname, strerror(errno));
105        return 1;
106    }
107
108    int found = 0;
109    char line[4096];
110    while (fgets(line, sizeof(line), input)) {
111        if (!should_tag(line, propname)) {
112            fputs(line, output);  // Pass through unmodified
113        } else {
114            found = 1;
115            int number = remove_tag(line, tag);
116            if (do_remove) {
117                fputs(line, output);  // Remove the tag but don't re-add it
118            } else {
119                write_tagged(output, line, tag, number + do_number);
120            }
121        }
122    }
123
124    fclose(input);
125    fclose(output);
126
127    if (!found) {
128        fprintf(stderr, "property %s not found in %s\n", propname, filename);
129        remove(tmpname);
130        return 1;
131    }
132
133    if (rename(tmpname, filename)) {
134        fprintf(stderr, "can't rename %s to %s: %s\n",
135            tmpname, filename, strerror(errno));
136        remove(tmpname);
137        return 1;
138    }
139
140    return 0;
141}
142