comparison: docs/Writerside/topics/streams.h.md
docs/Writerside/topics/streams.h.md
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| 1 # Data Streams | |
| 2 | |
| 3 Stream copy functions provide a way to copy all - or a limited amount of - data from one stream to another. | |
| 4 | |
| 5 Since the read/write functions of a [UCX buffer](buffer.h.md) are fully compatible with stream read/write functions, | |
| 6 you can, for example, easily transfer data from a file or network stream to a UCX buffer or vice versa. | |
| 7 | |
| 8 ## Overview | |
| 9 ```C | |
| 10 #include <cx/streams.h> | |
| 11 | |
| 12 size_t cx_stream_copy( | |
| 13 void *src, void *dest, | |
| 14 cx_read_func rfnc, cx_write_func wfnc | |
| 15 ); | |
| 16 size_t cx_stream_ncopy( | |
| 17 void *src, void *dest, | |
| 18 cx_read_func rfnc, cx_write_func wfnc, | |
| 19 size_t n | |
| 20 ); | |
| 21 | |
| 22 size_t cx_stream_bcopy( | |
| 23 void *src, void *dest, | |
| 24 cx_read_func rfnc, cx_write_func wfnc, | |
| 25 char *buf, size_t bufsize | |
| 26 ); | |
| 27 size_t cx_stream_bncopy( | |
| 28 void *src, void *dest, | |
| 29 cx_read_func rfnc, cx_write_func wfnc, | |
| 30 char *buf, size_t bufsize, | |
| 31 size_t n | |
| 32 ); | |
| 33 ``` | |
| 34 | |
| 35 ## Description | |
| 36 | |
| 37 All functions in the stream copy family use the `rfnc` to read data from `src` | |
| 38 and use the `wfnc` to write the data to `dest`. | |
| 39 | |
| 40 The `cx_stream_copy()` function always uses internal stack memory as a temporary buffer for the read bytes. | |
| 41 The `cx_stream_bcopy()` function uses either a pre-initialized buffer `buf` of length `bufsize` | |
| 42 or, if `buf` is `NULL`, an internal heap-allocated buffer. | |
| 43 | |
| 44 The `cx_stream_ncopy()` function behaves like `cx_stream_copy()` except, that it reads at most `n` bytes | |
| 45 (and the same is true for `cx_stream_bncopy()` and `cx_stream_bcopy()`). | |
| 46 | |
| 47 | |
| 48 <warning> | |
| 49 When you are reading from a stream where you cannot track the position, there is the possibility that | |
| 50 data gets lost when the destination does not accept all the bytes read from the source. | |
| 51 While the stream copy functions do report how many bytes were <emphasis>successfully</emphasis> copied | |
| 52 to the destination, this might - in certain cases - not be the exact number of read items. | |
| 53 | |
| 54 To mitigate the risk, you should make sure that the destination can always accept all read bytes and | |
| 55 a possible bottleneck is only introduced by the source. | |
| 56 </warning> | |
| 57 | |
| 58 > The size of the internal _stack_ buffer in `cx_stream_copy()` and `cx_stream_ncopy()` can be | |
| 59 > set during compilation via the `CX_STREAM_COPY_BUF_SIZE` macro. | |
| 60 > Similarly, the size for the implicitly allocated _heap_ buffer in can be | |
| 61 > configured via the `CX_STREAM_BCOPY_BUF_SIZE` macro. | |
| 62 > Refer to the [build instructions](install.md#compile-time-options) for the details. | |
| 63 | |
| 64 ## Example | |
| 65 | |
| 66 The following example shows, how to read the contents of a file into a buffer: | |
| 67 ```c | |
| 68 FILE *inputfile = fopen(infilename, "r"); | |
| 69 if (inputfile) { | |
| 70 CxBuffer fbuf; | |
| 71 cxBufferInit(&fbuf, NULL, 4096, NULL, CX_BUFFER_AUTO_EXTEND); | |
| 72 cx_stream_copy(inputfile, &fbuf, | |
| 73 (cx_read_func) fread, | |
| 74 cxBufferWriteFunc); | |
| 75 fclose(inputfile); | |
| 76 | |
| 77 // ... do something meaningful with the contents ... | |
| 78 | |
| 79 cxBufferDestroy(&fbuf); | |
| 80 } else { | |
| 81 perror("Error opening input file"); | |
| 82 } | |
| 83 ``` | |
| 84 | |
| 85 | |
| 86 <seealso> | |
| 87 <category ref="apidoc"> | |
| 88 <a href="https://ucx.sourceforge.io/api/streams_8h.html">streams.h</a> | |
| 89 </category> | |
| 90 </seealso> |
