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 /*

  * 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;

     }

 }

 size_t cxBufferWrite(

         void const *ptr,

         size_t size,

         size_t nitems,

         CxBuffer *buffer

 ) {

     // TODO: optimize for special case size == nitems == 1

     size_t len;

     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 = len / size;

             }

         }

     }

     if (len == 0) {

         return len;

     }

     if (perform_flush) {

         // TODO: implement flushing

         // (1) determine how many bytes to flush (use flushmax = blkmax * blksize)

         // (2) if len is larger than the number computed in (1) we need more flush cycles, compute how many

         // (3) determine how many bytes from the buffer shall be flushed

         // (4) if something remains in the buffer, shift the buffer to the left

         // (4a) if buffer was shifted, append the new data to the buffer

         // (4b) if the buffer was flushed entirely AND the new data also fits into flushmax,

         //      directly write the new data to the flush sink

         return 0; // remove this after implementation

     } else {

         memcpy(buffer->bytes + buffer->pos, ptr, len);

         buffer->pos += len;

         if (buffer->pos > buffer->size) {

             buffer->size = buffer->pos;

         }

     }

     return nitems;

 }

 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;

     }

 }