1ZIP_SOURCE_FUNCTION(3) BSD Library Functions Manual ZIP_SOURCE_FUNCTION(3)
2
4 zip_source_function, zip_source_function_create — create data source from
5 function
6
8 libzip (-lzip)
9
11 #include <zip.h>
12 zip_source_t *
14 zip_source_function(zip_t *archive, zip_source_callback fn,
15 void *userdata);
16 zip_source_t *
18 zip_source_function_create(zip_source_callback fn, void *userdata,
19 zip_error_t *error);
20
22 The functions zip_source_function() and zip_source_function_create() cre‐
23 ates a zip source from the user-provided function fn, which must be of
24 the following type:
25 typedef zip_int64_t (*zip_source_callback)(void *userdata, void *data,
27 zip_uint64_t len, zip_source_cmd_t cmd)
28 archive or error are used for reporting errors and can be NULL.
30 When called by the library, the first argument is the userdata argument
32 supplied to the function. The next two arguments are a buffer data of
33 size len when data is passed in or expected to be returned, or else NULL
34 and 0. The last argument, cmd, specifies which action the function
35 should perform.
36 Depending on the uses, there are three useful sets of commands to be sup‐
38 ported by a zip_source_callback():
39 read source Providing streamed data (for file data added to
41 archives). Must support ZIP_SOURCE_OPEN,
42 ZIP_SOURCE_READ, ZIP_SOURCE_CLOSE,
43 ZIP_SOURCE_STAT, and ZIP_SOURCE_ERROR.
44 seekable read source Same as previous, but from a source allowing
46 reading from arbitrary offsets (also for read-
47 only zip archive). Must additionally support
48 ZIP_SOURCE_SEEK, ZIP_SOURCE_TELL, and
49 ZIP_SOURCE_SUPPORTS.
50 read/write source Same as previous, but additionally allowing writ‐
52 ing (also for writable zip archives). Must addi‐
53 tionally support ZIP_SOURCE_BEGIN_WRITE,
54 ZIP_SOURCE_COMMIT_WRITE,
55 ZIP_SOURCE_ROLLBACK_WRITE, ZIP_SOURCE_SEEK_WRITE,
56 ZIP_SOURCE_TELL_WRITE, and ZIP_SOURCE_REMOVE.
57 ZIP_SOURCE_ACCEPT_EMPTY
59 Return 1 if an empty source should be accepted as a valid zip archive.
60 This is the default if this command is not supported by a source. File
61 system backed sources should return 0.
62 ZIP_SOURCE_BEGIN_WRITE
64 Prepare the source for writing. Use this to create any temporary
65 file(s).
66 ZIP_SOURCE_BEGIN_WRITE_CLONING
68 Prepare the source for writing, keeping the first len bytes of the origi‐
69 nal file. Only implement this command if it is more efficient than copy‐
70 ing the data, and if it does not destructively overwrite the original
71 file (you still have to be able to execute ZIP_SOURCE_ROLLBACK_WRITE).
72 The next write should happen at byte offset.
74 ZIP_SOURCE_CLOSE
76 Reading is done.
77 ZIP_SOURCE_COMMIT_WRITE
79 Finish writing to the source. Replace the original data with the newly
80 written data. Clean up temporary files or internal buffers. Subse‐
81 quently opening and reading from the source should return the newly writ‐
82 ten data.
83 ZIP_SOURCE_ERROR
85 Get error information. data points to an array of two ints, which should
86 be filled with the libzip error code and the corresponding system error
87 code for the error that occurred. See zip_errors(3) for details on the
88 error codes. If the source stores error information in a zip_error_t,
89 use zip_error_to_data(3) and return its return value. Otherwise, return
90 2 * sizeof(int).
91 ZIP_SOURCE_FREE
93 Clean up and free all resources, including userdata. The callback func‐
94 tion will not be called again.
95 ZIP_SOURCE_OPEN
97 Prepare for reading.
98 ZIP_SOURCE_READ
100 Read data into the buffer data of size len. Return the number of bytes
101 placed into data on success, and zero for end-of-file.
102 ZIP_SOURCE_REMOVE
104 Remove the underlying file. This is called if a zip archive is empty
105 when closed.
106 ZIP_SOURCE_ROLLBACK_WRITE
108 Abort writing to the source. Discard written data. Clean up temporary
109 files or internal buffers. Subsequently opening and reading from the
110 source should return the original data.
111 ZIP_SOURCE_SEEK
113 Specify position to read next byte from, like fseek(3). Use
114 ZIP_SOURCE_GET_ARGS(3) to decode the arguments into the following struct:
115 struct zip_source_args_seek {
117 zip_int64_t offset;
118 int whence;
119 };
120 If the size of the source's data is known, use
122 zip_source_seek_compute_offset(3) to validate the arguments and compute
123 the new offset.
124 ZIP_SOURCE_SEEK_WRITE
126 Specify position to write next byte to, like fseek(3). See
127 ZIP_SOURCE_SEEK for details.
128 ZIP_SOURCE_STAT
130 Get meta information for the input data. data points to an allocated
131 struct zip_stat, which should be initialized using zip_stat_init(3) and
132 then filled in.
133 For uncompressed, unencrypted data, all information is optional. How‐
135 ever, fill in as much information as is readily available.
136 If the data is compressed, ZIP_STAT_COMP_METHOD, ZIP_STAT_SIZE, and
138 ZIP_STAT_CRC must be filled in.
139 If the data is encrypted, ZIP_STAT_ENCRYPTION_METHOD,
141 ZIP_STAT_COMP_METHOD, ZIP_STAT_SIZE, and ZIP_STAT_CRC must be filled in.
142 Information only available after the source has been read (e.g., size)
144 can be omitted in an earlier call. NOTE: zip_source_function() may be
145 called with this argument even after being called with ZIP_SOURCE_CLOSE.
146 Return sizeof(struct zip_stat) on success.
148 ZIP_SOURCE_SUPPORTS
150 Return bitmap specifying which commands are supported. Use
151 zip_source_make_command_bitmap(3). If this command is not implemented,
152 the source is assumed to be a read source without seek support.
153 ZIP_SOURCE_TELL
155 Return the current read offset in the source, like ftell(3).
156 ZIP_SOURCE_TELL_WRITE
158 Return the current write offset in the source, like ftell(3).
159 ZIP_SOURCE_WRITE
161 Write data to the source. Return number of bytes written.
162 Return Values
164 Commands should return -1 on error. ZIP_SOURCE_ERROR will be called to
165 retrieve the error code. On success, commands return 0, unless specified
166 otherwise in the description above.
167 Calling Conventions
169 The library will always issue ZIP_SOURCE_OPEN before issuing
170 ZIP_SOURCE_READ, ZIP_SOURCE_SEEK, or ZIP_SOURCE_TELL. When it no longer
171 wishes to read from this source, it will issue ZIP_SOURCE_CLOSE. If the
172 library wishes to read the data again, it will issue ZIP_SOURCE_OPEN a
173 second time. If the function is unable to provide the data again, it
174 should return -1.
175 ZIP_SOURCE_BEGIN_WRITE or ZIP_SOURCE_BEGIN_WRITE_CLONING will be called
177 before ZIP_SOURCE_WRITE, ZIP_SOURCE_SEEK_WRITE, or ZIP_SOURCE_TELL_WRITE.
178 When writing is complete, either ZIP_SOURCE_COMMIT_WRITE or
179 ZIP_SOURCE_ROLLBACK_WRITE will be called.
180 ZIP_SOURCE_STAT can be issued at any time.
182 ZIP_SOURCE_ERROR will only be issued in response to the function return‐
184 ing -1.
185 ZIP_SOURCE_FREE will be the last command issued; if ZIP_SOURCE_OPEN was
187 called and succeeded, ZIP_SOURCE_CLOSE will be called before
188 ZIP_SOURCE_FREE, and similarly for ZIP_SOURCE_BEGIN_WRITE or
189 ZIP_SOURCE_BEGIN_WRITE_CLONING and ZIP_SOURCE_COMMIT_WRITE or
190 ZIP_SOURCE_ROLLBACK_WRITE.
191
193 Upon successful completion, the created source is returned. Otherwise,
194 NULL is returned and the error code in archive or error is set to indi‐
195 cate the error (unless it is NULL).
196
198 zip_source_function() fails if:
199 [ZIP_ER_MEMORY] Required memory could not be allocated.
201
203 libzip(3), zip_file_add(3), zip_file_replace(3), zip_source(3),
204 zip_stat_init(3)
205
207 zip_source_function() and zip_source_function_create() were added in
208 libzip 1.0.
209
211 Dieter Baron <dillo@nih.at> and Thomas Klausner <tk@giga.or.at>
212BSD September 17, 2019 BSD