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ZCHUNK(3) CZMQ Manual ZCHUNK(3) NAME zchunk - Class for work with memory chunks SYNOPSIS // This is a stable class, and may not change except for emergencies. It // is provided in stable builds. // This class has draft methods, which may change over time. They are not // in stable releases, by default. Use --enable-drafts to enable. // Create a new chunk of the specified size. If you specify the data, it // is copied into the chunk. If you do not specify the data, the chunk is // allocated and left empty, and you can then add data using zchunk_append. CZMQ_EXPORT zchunk_t * zchunk_new (const void *data, size_t size); // Destroy a chunk CZMQ_EXPORT void zchunk_destroy (zchunk_t **self_p); // Resizes chunk max_size as requested; chunk_cur size is set to zero CZMQ_EXPORT void zchunk_resize (zchunk_t *self, size_t size); // Return chunk cur size CZMQ_EXPORT size_t zchunk_size (zchunk_t *self); // Return chunk max size CZMQ_EXPORT size_t zchunk_max_size (zchunk_t *self); // Return chunk data CZMQ_EXPORT byte * zchunk_data (zchunk_t *self); // Set chunk data from user-supplied data; truncate if too large. Data may // be null. Returns actual size of chunk CZMQ_EXPORT size_t zchunk_set (zchunk_t *self, const void *data, size_t size); // Fill chunk data from user-supplied octet CZMQ_EXPORT size_t zchunk_fill (zchunk_t *self, byte filler, size_t size); // Append user-supplied data to chunk, return resulting chunk size. If the // data would exceeded the available space, it is truncated. If you want to // grow the chunk to accommodate new data, use the zchunk_extend method. CZMQ_EXPORT size_t zchunk_append (zchunk_t *self, const void *data, size_t size); // Append user-supplied data to chunk, return resulting chunk size. If the // data would exceeded the available space, the chunk grows in size. CZMQ_EXPORT size_t zchunk_extend (zchunk_t *self, const void *data, size_t size); // Copy as much data from 'source' into the chunk as possible; returns the // new size of chunk. If all data from 'source' is used, returns exhausted // on the source chunk. Source can be consumed as many times as needed until // it is exhausted. If source was already exhausted, does not change chunk. CZMQ_EXPORT size_t zchunk_consume (zchunk_t *self, zchunk_t *source); // Returns true if the chunk was exhausted by consume methods, or if the // chunk has a size of zero. CZMQ_EXPORT bool zchunk_exhausted (zchunk_t *self); // Read chunk from an open file descriptor // Caller owns return value and must destroy it when done. CZMQ_EXPORT zchunk_t * zchunk_read (FILE *handle, size_t bytes); // Write chunk to an open file descriptor CZMQ_EXPORT int zchunk_write (zchunk_t *self, FILE *handle); // Try to slurp an entire file into a chunk. Will read up to maxsize of // the file. If maxsize is 0, will attempt to read the entire file and // fail with an assertion if that cannot fit into memory. Returns a new // chunk containing the file data, or NULL if the file could not be read. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zchunk_t * zchunk_slurp (const char *filename, size_t maxsize); // Create copy of chunk, as new chunk object. Returns a fresh zchunk_t // object, or null if there was not enough heap memory. If chunk is null, // returns null. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zchunk_t * zchunk_dup (zchunk_t *self); // Return chunk data encoded as printable hex string. Caller must free // string when finished with it. // Caller owns return value and must destroy it when done. CZMQ_EXPORT char * zchunk_strhex (zchunk_t *self); // Return chunk data copied into freshly allocated string // Caller must free string when finished with it. // Caller owns return value and must destroy it when done. CZMQ_EXPORT char * zchunk_strdup (zchunk_t *self); // Return TRUE if chunk body is equal to string, excluding terminator CZMQ_EXPORT bool zchunk_streq (zchunk_t *self, const char *string); // Transform zchunk into a zframe that can be sent in a message. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zframe_t * zchunk_pack (zchunk_t *self); // Transform a zframe into a zchunk. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zchunk_t * zchunk_unpack (zframe_t *frame); // Calculate SHA1 digest for chunk, using zdigest class. CZMQ_EXPORT const char * zchunk_digest (zchunk_t *self); // Dump chunk to FILE stream, for debugging and tracing. CZMQ_EXPORT void zchunk_fprint (zchunk_t *self, FILE *file); // Dump message to stderr, for debugging and tracing. // See zchunk_fprint for details CZMQ_EXPORT void zchunk_print (zchunk_t *self); // Probe the supplied object, and report if it looks like a zchunk_t. CZMQ_EXPORT bool zchunk_is (void *self); // Self test of this class. CZMQ_EXPORT void zchunk_test (bool verbose); #ifdef CZMQ_BUILD_DRAFT_API // Destroy an item typedef void (zchunk_destructor_fn) ( void **hint); // *** Draft method, for development use, may change without warning *** // Create a new chunk from memory. Take ownership of the memory and calling the destructor // on destroy. CZMQ_EXPORT zchunk_t * zchunk_frommem (void *data, size_t size, zchunk_destructor_fn destructor, void *hint); // *** Draft method, for development use, may change without warning *** // Transform zchunk into a zframe that can be sent in a message. // Take ownership of the chunk. // Caller owns return value and must destroy it when done. CZMQ_EXPORT zframe_t * zchunk_packx (zchunk_t **self_p); #endif // CZMQ_BUILD_DRAFT_API Please add '@interface' section in './../src/zchunk.c'. DESCRIPTION The zchunk class works with variable sized blobs. Not as efficient as ZeroMQ's messages but they do less weirdness and so are easier to understand. The chunk class has methods to read and write chunks from disk. Please add @discuss section in ./../src/zchunk.c. EXAMPLE From zchunk_test method. zchunk_t *chunk = zchunk_new ("1234567890", 10); assert (chunk); assert (zchunk_size (chunk) == 10); assert (memcmp (zchunk_data (chunk), "1234567890", 10) == 0); zchunk_destroy (&chunk); chunk = zchunk_new (NULL, 10); assert (chunk); zchunk_append (chunk, "12345678", 8); zchunk_append (chunk, "90ABCDEF", 8); zchunk_append (chunk, "GHIJKLMN", 8); assert (memcmp (zchunk_data (chunk), "1234567890", 10) == 0); assert (zchunk_size (chunk) == 10); assert (zchunk_streq (chunk, "1234567890")); assert (streq (zchunk_digest (chunk), "01B307ACBA4F54F55AAFC33BB06BBBF6CA803E9A")); char *string = zchunk_strdup (chunk); assert (streq (string, "1234567890")); freen (string); string = zchunk_strhex (chunk); assert (streq (string, "31323334353637383930")); freen (string); zframe_t *frame = zchunk_pack (chunk); assert (frame); zchunk_t *chunk2 = zchunk_unpack (frame); assert (chunk2); assert (memcmp (zchunk_data (chunk2), "1234567890", 10) == 0); zframe_destroy (&frame); zchunk_destroy (&chunk2); zchunk_t *copy = zchunk_dup (chunk); assert (copy); assert (memcmp (zchunk_data (copy), "1234567890", 10) == 0); assert (zchunk_size (copy) == 10); zchunk_destroy (©); zchunk_destroy (&chunk); chunk = zchunk_new (NULL, 0); zchunk_extend (chunk, "12345678", 8); zchunk_extend (chunk, "90ABCDEF", 8); zchunk_extend (chunk, "GHIJKLMN", 8); assert (zchunk_size (chunk) == 24); assert (zchunk_streq (chunk, "1234567890ABCDEFGHIJKLMN")); zchunk_destroy (&chunk); copy = zchunk_new ("1234567890abcdefghij", 20); assert (copy); chunk = zchunk_new (NULL, 8); assert (chunk); zchunk_consume (chunk, copy); assert (!zchunk_exhausted (copy)); assert (memcmp (zchunk_data (chunk), "12345678", 8) == 0); zchunk_set (chunk, NULL, 0); zchunk_consume (chunk, copy); assert (!zchunk_exhausted (copy)); assert (memcmp (zchunk_data (chunk), "90abcdef", 8) == 0); zchunk_set (chunk, NULL, 0); zchunk_consume (chunk, copy); assert (zchunk_exhausted (copy)); assert (zchunk_size (chunk) == 4); assert (memcmp (zchunk_data (chunk), "ghij", 4) == 0); zchunk_destroy (©); zchunk_destroy (&chunk); char str[] = "hello"; chunk = zchunk_frommem (str, 5, mem_destructor, str); assert (chunk); zchunk_destroy (&chunk); // The destructor doesn't free the memory, only changing the strid, // so we can check if the destructor was invoked assert (streq (str, "world")); chunk = zchunk_new ("1234567890", 10); frame = zchunk_packx (&chunk); assert (frame); assert (chunk == NULL); chunk = zchunk_unpack (frame); assert (chunk); assert (memcmp (zchunk_data (chunk), "1234567890", 10) == 0); zframe_destroy (&frame); zchunk_destroy (&chunk); #if defined (__WINDOWS__) zsys_shutdown(); #endif AUTHORS The czmq manual was written by the authors in the AUTHORS file. RESOURCES Main web site: Report bugs to the email <zeromq-dev@lists.zeromq.org[1]> COPYRIGHT Copyright (c) the Contributors as noted in the AUTHORS file. This file is part of CZMQ, the high-level C binding for 0MQ: http://czmq.zeromq.org. This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/. LICENSE included with the czmq distribution. NOTES 1. zeromq-dev@lists.zeromq.org mailto:zeromq-dev@lists.zeromq.org CZMQ 4.2.1 11/01/2025 ZCHUNK(3)
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