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_GET_FILE_ATTRIBUTES
97 Provide information about various data. Then the data should be put in
98 the appropriate entry in the passed zip_file_attributes_t argument, and
99 the appropriate ZIP_FILE_ATTRIBUTES_* value must be or'ed into the valid
100 member to denote that the corresponding data has been provided. A
101 zip_file_attributes_t structure can be initialized using
102 zip_file_attributes_init(3).
103 ASCII mode If a file is a plaintext file in ASCII. Can be used by
105 extraction tools to automatically convert line endings (part
106 of the interal file attributes). Member ascii, flag
107 ZIP_FILE_ATTRIBUTES_ASCII.
108 General Purpose Bit Flags (limited to Compression Flags)
110 The general purpose bit flag in the zip in the local and cen‐
111 tral directory headers contain information about the compres‐
112 sion method. Member general_purpose_bit_flags and
113 general_purpose_bit_mask to denote which members have been
114 set; flag ZIP_FILE_ATTRIBUTES_GENERAL_PURPOSE_BIT_FLAGS.
115 External File Attributes
117 The external file attributes (usually operating system-spe‐
118 cific). Member external_file_attributes, flag
119 ZIP_FILE_ATTRIBUTES_EXTERNAL_FILE_ATTRIBUTES.
120 Version Needed
122 A minimum version needed required to unpack this entry (in
123 the usual "major * 10 + minor" format). Member
124 version_needed, flag ZIP_FILE_ATTRIBUTES_VERSION_NEEDED.
125 Operating System
127 One of the operating systems as defined by the ZIP_OPSYS_*
128 variables (see zip.h). This value affects the interpretation
129 of the external file attributes. Member host_system, flag
130 ZIP_FILE_ATTRIBUTES_HOST_SYSTEM.
131 ZIP_SOURCE_OPEN
133 Prepare for reading.
134 ZIP_SOURCE_READ
136 Read data into the buffer data of size len. Return the number of bytes
137 placed into data on success, and zero for end-of-file.
138 ZIP_SOURCE_REMOVE
140 Remove the underlying file. This is called if a zip archive is empty
141 when closed.
142 ZIP_SOURCE_ROLLBACK_WRITE
144 Abort writing to the source. Discard written data. Clean up temporary
145 files or internal buffers. Subsequently opening and reading from the
146 source should return the original data.
147 ZIP_SOURCE_SEEK
149 Specify position to read next byte from, like fseek(3). Use
150 ZIP_SOURCE_GET_ARGS(3) to decode the arguments into the following struct:
151 struct zip_source_args_seek {
153 zip_int64_t offset;
154 int whence;
155 };
156 If the size of the source's data is known, use
158 zip_source_seek_compute_offset(3) to validate the arguments and compute
159 the new offset.
160 ZIP_SOURCE_SEEK_WRITE
162 Specify position to write next byte to, like fseek(3). See
163 ZIP_SOURCE_SEEK for details.
164 ZIP_SOURCE_STAT
166 Get meta information for the input data. data points to an allocated
167 struct zip_stat, which should be initialized using zip_stat_init(3) and
168 then filled in.
169 For uncompressed, unencrypted data, all information is optional. How‐
171 ever, fill in as much information as is readily available.
172 If the data is compressed, ZIP_STAT_COMP_METHOD, ZIP_STAT_SIZE, and
174 ZIP_STAT_CRC must be filled in.
175 If the data is encrypted, ZIP_STAT_ENCRYPTION_METHOD,
177 ZIP_STAT_COMP_METHOD, ZIP_STAT_SIZE, and ZIP_STAT_CRC must be filled in.
178 Information only available after the source has been read (e.g., size)
180 can be omitted in an earlier call. NOTE: zip_source_function() may be
181 called with this argument even after being called with ZIP_SOURCE_CLOSE.
182 Return sizeof(struct zip_stat) on success.
184 ZIP_SOURCE_SUPPORTS
186 Return bitmap specifying which commands are supported. Use
187 zip_source_make_command_bitmap(3). If this command is not implemented,
188 the source is assumed to be a read source without seek support.
189 ZIP_SOURCE_TELL
191 Return the current read offset in the source, like ftell(3).
192 ZIP_SOURCE_TELL_WRITE
194 Return the current write offset in the source, like ftell(3).
195 ZIP_SOURCE_WRITE
197 Write data to the source. Return number of bytes written.
198 Return Values
200 Commands should return -1 on error. ZIP_SOURCE_ERROR will be called to
201 retrieve the error code. On success, commands return 0, unless specified
202 otherwise in the description above.
203 Calling Conventions
205 The library will always issue ZIP_SOURCE_OPEN before issuing
206 ZIP_SOURCE_READ, ZIP_SOURCE_SEEK, or ZIP_SOURCE_TELL. When it no longer
207 wishes to read from this source, it will issue ZIP_SOURCE_CLOSE. If the
208 library wishes to read the data again, it will issue ZIP_SOURCE_OPEN a
209 second time. If the function is unable to provide the data again, it
210 should return -1.
211 ZIP_SOURCE_BEGIN_WRITE or ZIP_SOURCE_BEGIN_WRITE_CLONING will be called
213 before ZIP_SOURCE_WRITE, ZIP_SOURCE_SEEK_WRITE, or ZIP_SOURCE_TELL_WRITE.
214 When writing is complete, either ZIP_SOURCE_COMMIT_WRITE or
215 ZIP_SOURCE_ROLLBACK_WRITE will be called.
216 ZIP_SOURCE_ACCEPT_EMPTY, ZIP_SOURCE_GET_FILE_ATTRIBUTES, and
218 ZIP_SOURCE_STAT can be issued at any time.
219 ZIP_SOURCE_ERROR will only be issued in response to the function return‐
221 ing -1.
222 ZIP_SOURCE_FREE will be the last command issued; if ZIP_SOURCE_OPEN was
224 called and succeeded, ZIP_SOURCE_CLOSE will be called before
225 ZIP_SOURCE_FREE, and similarly for ZIP_SOURCE_BEGIN_WRITE or
226 ZIP_SOURCE_BEGIN_WRITE_CLONING and ZIP_SOURCE_COMMIT_WRITE or
227 ZIP_SOURCE_ROLLBACK_WRITE.
228
230 Upon successful completion, the created source is returned. Otherwise,
231 NULL is returned and the error code in archive or error is set to indi‐
232 cate the error (unless it is NULL).
233
235 zip_source_function() fails if:
236 [ZIP_ER_MEMORY] Required memory could not be allocated.
238
240 libzip(3), zip_file_add(3), zip_file_attributes_init(3),
241 zip_file_replace(3), zip_source(3), zip_stat_init(3)
242
244 zip_source_function() and zip_source_function_create() were added in
245 libzip 1.0.
246
248 Dieter Baron <dillo@nih.at> and Thomas Klausner <tk@giga.or.at>
249BSD April 17, 2020 BSD