ucx: src/buffer.c@2e73456e5f84 (annotated)

src/buffer.c@2e73456e5f84 (annotated)

src/buffer.c

Sun, 01 May 2022 13:14:31 +0200

author: Mike Becker <universe@uap-core.de>
date: Sun, 01 May 2022 13:14:31 +0200
changeset 544: 2e73456e5f84
parent 543: 7b9114030ca4
child 567: f90a7cfe2480
permissions: -rw-r--r--

#184 untested implementation of the flush feature

 /*
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
  *
  * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *   1. Redistributions of source code must retain the above copyright
  *      notice, this list of conditions and the following disclaimer.
  *
  *   2. Redistributions in binary form must reproduce the above copyright
  *      notice, this list of conditions and the following disclaimer in the
  *      documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */
 #include "cx/buffer.h"
 #include "cx/utils.h"
 #include <stdlib.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdint.h>
 int cxBufferInit(
         CxBuffer *buffer,
         void *space,
         size_t capacity,
         CxAllocator const *allocator,
         int flags
 ) {
     buffer->allocator = allocator;
     buffer->flags = flags;
     if (!space) {
         buffer->bytes = cxMalloc(allocator, capacity);
         if (buffer->bytes == NULL) {
             return 1;
         }
         buffer->flags |= CX_BUFFER_FREE_CONTENTS;
     } else {
         buffer->bytes = space;
     }
     buffer->capacity = capacity;
     buffer->size = 0;
     buffer->pos = 0;
     buffer->flush_func = NULL;
     buffer->flush_target = NULL;
     buffer->flush_blkmax = 0;
     buffer->flush_blksize = 4096;
     buffer->flush_threshold = SIZE_MAX;
     return 0;
 }
 void cxBufferDestroy(CxBuffer *buffer) {
     if ((buffer->flags & CX_BUFFER_FREE_CONTENTS) == CX_BUFFER_FREE_CONTENTS) {
         cxFree(buffer->allocator, buffer->bytes);
     }
 }
 int cxBufferSeek(
         CxBuffer *buffer,
         off_t offset,
         int whence
 ) {
     size_t npos;
     switch (whence) {
         case SEEK_CUR:
             npos = buffer->pos;
             break;
         case SEEK_END:
             npos = buffer->size;
             break;
         case SEEK_SET:
             npos = 0;
             break;
         default:
             return -1;
     }
     size_t opos = npos;
     npos += offset;
     if ((offset > 0 && npos < opos) || (offset < 0 && npos > opos)) {
         return -1;
     }
     if (npos >= buffer->size) {
         return -1;
     } else {
         buffer->pos = npos;
         return 0;
     }
 }
 void cxBufferClear(CxBuffer *buffer) {
     memset(buffer->bytes, 0, buffer->size);
     buffer->size = 0;
     buffer->pos = 0;
 }
 int cxBufferEof(CxBuffer const *buffer) {
     return buffer->pos >= buffer->size;
 }
 int cxBufferMinimumCapacity(
         CxBuffer *buffer,
         size_t newcap
 ) {
     if (newcap <= buffer->capacity) {
         return 0;
     }
     if (cxReallocate(buffer->allocator,
                      (void **) &buffer->bytes, newcap) == 0) {
         buffer->capacity = newcap;
         return 0;
     } else {
         return -1;
     }
 }
 /**
  * Helps flushing data to the flush target of a buffer.
  *
  * @param buffer the buffer containing the config
  * @param space the data to flush
  * @param size the element size
  * @param nitems the number of items
  * @return the number of items flushed
  */
 static size_t cx_buffer_write_flush_helper(
         CxBuffer *buffer,
         unsigned char const *space,
         size_t size,
         size_t nitems
 ) {
     size_t pos = 0;
     size_t remaining = nitems;
     size_t max_items = buffer->flush_blksize / size;
     while (remaining > 0) {
         size_t items = remaining > max_items ? max_items : remaining;
         size_t flushed = buffer->flush_func(
                 space + pos,
                 size, items,
                 buffer->flush_target);
         if (flushed > 0) {
             pos += (flushed * size);
             remaining -= flushed;
         } else {
             // if no bytes can be flushed out anymore, we give up
             break;
         }
     }
     return nitems - remaining;
 }
 size_t cxBufferWrite(
         void const *ptr,
         size_t size,
         size_t nitems,
         CxBuffer *buffer
 ) {
     // optimize for easy case
     if (size == 1 && (buffer->capacity - buffer->pos) >= nitems) {
         memcpy(buffer->bytes + buffer->pos, ptr, nitems);
         buffer->pos += nitems;
         if (buffer->pos > buffer->size) {
             buffer->size = buffer->pos;
         }
         return nitems;
     }
     size_t len;
     size_t nitems_out = nitems;
     if (cx_szmul(size, nitems, &len)) {
         return 0;
     }
     size_t required = buffer->pos + len;
     if (buffer->pos > required) {
         return 0;
     }
     bool perform_flush = false;
     if (required > buffer->capacity) {
         if ((buffer->flags & CX_BUFFER_AUTO_EXTEND) == CX_BUFFER_AUTO_EXTEND && required) {
             if (buffer->flush_blkmax > 0 && required > buffer->flush_threshold) {
                 perform_flush = true;
             } else {
                 if (cxBufferMinimumCapacity(buffer, required)) {
                     return 0;
                 }
             }
         } else {
             if (buffer->flush_blkmax > 0) {
                 perform_flush = true;
             } else {
                 // truncate data to be written, if we can neither extend nor flush
                 len = buffer->capacity - buffer->pos;
                 if (size > 1) {
                     len -= len % size;
                 }
                 nitems_out = len / size;
             }
         }
     }
     if (len == 0) {
         return len;
     }
     if (perform_flush) {
         size_t flush_max;
         if (cx_szmul(buffer->flush_blkmax, buffer->flush_blksize, &flush_max)) {
             return 0;
         }
         size_t flush_pos = buffer->flush_func == NULL || buffer->flush_target == NULL
                            ? buffer->pos
                            : cx_buffer_write_flush_helper(buffer, buffer->bytes, 1, buffer->pos);
         if (flush_pos == buffer->pos) {
             // entire buffer has been flushed, we can reset
             buffer->size = buffer->pos = 0;
             size_t items_flush; // how many items can also be directly flushed
             size_t items_keep; // how many items have to be written to the buffer
             items_flush = flush_max >= required ? nitems : (flush_max - flush_pos) / size;
             if (items_flush > 0) {
                 items_flush = cx_buffer_write_flush_helper(buffer, ptr, size, items_flush / size);
                 // in case we could not flush everything, keep the rest
             }
             items_keep = nitems - items_flush;
             if (items_keep > 0) {
                 // try again with the remaining stuff
                 unsigned char const *new_ptr = ptr;
                 new_ptr += items_flush * size;
                 return cxBufferWrite(new_ptr, size, items_keep, buffer);
             } else {
                 // all items have been flushed - report them as written
                 return nitems;
             }
         } else if (flush_pos == 0) {
             // nothing could be flushed at all, we immediately give up without writing any data
             return 0;
         } else {
             // we were partially successful, we have shift left and try again
             cxBufferShiftLeft(buffer, flush_pos);
             return cxBufferWrite(ptr, size, nitems, buffer);
         }
     } else {
         memcpy(buffer->bytes + buffer->pos, ptr, len);
         buffer->pos += len;
         if (buffer->pos > buffer->size) {
             buffer->size = buffer->pos;
         }
         return nitems_out;
     }
 }
 int cxBufferPut(
         CxBuffer *buffer,
         int c
 ) {
     c &= 0xFF;
     unsigned char const ch = c;
     if (cxBufferWrite(&ch, 1, 1, buffer) == 1) {
         return c;
     } else {
         return EOF;
     }
 }
 size_t cxBufferPutString(
         CxBuffer *buffer,
         const char *str
 ) {
     return cxBufferWrite(str, 1, strlen(str), buffer);
 }
 size_t cxBufferRead(
         void *ptr,
         size_t size,
         size_t nitems,
         CxBuffer *buffer
 ) {
     size_t len;
     if (cx_szmul(size, nitems, &len)) {
         return 0;
     }
     if (buffer->pos + len > buffer->size) {
         len = buffer->size - buffer->pos;
         if (size > 1) len -= len % size;
     }
     if (len <= 0) {
         return len;
     }
     memcpy(ptr, buffer->bytes + buffer->pos, len);
     buffer->pos += len;
     return len / size;
 }
 int cxBufferGet(CxBuffer *buffer) {
     if (cxBufferEof(buffer)) {
         return EOF;
     } else {
         int c = buffer->bytes[buffer->pos];
         buffer->pos++;
         return c;
     }
 }
 int cxBufferShiftLeft(
         CxBuffer *buffer,
         size_t shift
 ) {
     if (shift >= buffer->size) {
         buffer->pos = buffer->size = 0;
     } else {
         memmove(buffer->bytes, buffer->bytes + shift, buffer->size - shift);
         buffer->size -= shift;
         if (buffer->pos >= shift) {
             buffer->pos -= shift;
         } else {
             buffer->pos = 0;
         }
     }
     return 0;
 }
 int cxBufferShiftRight(
         CxBuffer *buffer,
         size_t shift
 ) {
     size_t req_capacity = buffer->size + shift;
     size_t movebytes;
     // auto extend buffer, if required and enabled
     if (buffer->capacity < req_capacity) {
         if ((buffer->flags & CX_BUFFER_AUTO_EXTEND) == CX_BUFFER_AUTO_EXTEND) {
             if (cxBufferMinimumCapacity(buffer, req_capacity)) {
                 return 1;
             }
             movebytes = buffer->size;
         } else {
             movebytes = buffer->capacity - shift;
         }
     } else {
         movebytes = buffer->size;
     }
     memmove(buffer->bytes + shift, buffer->bytes, movebytes);
     buffer->size = shift + movebytes;
     buffer->pos += shift;
     if (buffer->pos > buffer->size) {
         buffer->pos = buffer->size;
     }
     return 0;
 }
 int cxBufferShift(
         CxBuffer *buffer,
         off_t shift
 ) {
     if (shift < 0) {
         return cxBufferShiftLeft(buffer, (size_t) (-shift));
     } else if (shift > 0) {
         return cxBufferShiftRight(buffer, (size_t) shift);
     } else {
         return 0;
     }
 }

Mercurial > hg > ucx / annotate

src/buffer.c@2e73456e5f84 (annotated)

src/buffer.c