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 /*

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

  *

  * Copyright 2017 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.

  */

 /**

  * @file buffer.h

  * 

  * Advanced buffer implementation.

  * 

  * Instances of UcxBuffer can be used to read from or to write to like one

  * would do with a stream. This allows the use of ucx_stream_copy() to copy

  * contents from one buffer to another.

  * 

  * Some features for convenient use of the buffer

  * can be enabled. See the documentation of the macro constants for more

  * information.

  * 

  * @author Mike Becker

  * @author Olaf Wintermann

  */

 #ifndef UCX_BUFFER_H

 #define	UCX_BUFFER_H

 #include "ucx.h"

 #include <sys/types.h>

 #include <stdio.h>

 #ifdef	__cplusplus

 extern "C" {

 #endif

 /**

  * No buffer features enabled (all flags cleared).

  */

 #define UCX_BUFFER_DEFAULT      0x00

 /**

  * If this flag is enabled, the buffer will automatically free its contents.

  */

 #define UCX_BUFFER_AUTOFREE     0x01

 /**

  * If this flag is enabled, the buffer will automatically extends its capacity.

  */

 #define UCX_BUFFER_AUTOEXTEND   0x02

 /** UCX Buffer. */

 typedef struct {

     /** A pointer to the buffer contents. */

     char *space;

     /** Current position of the buffer. */

     size_t pos;

     /** Current capacity (i.e. maximum size) of the buffer. */

     size_t capacity;

     /** Current size of the buffer content. */

     size_t size;

     /**

      * Flag register for buffer features.

      * @see #UCX_BUFFER_DEFAULT

      * @see #UCX_BUFFER_AUTOFREE

      * @see #UCX_BUFFER_AUTOEXTEND

      */

     int flags;

 } UcxBuffer;

 /**

  * Creates a new buffer.

  * 

  * <b>Note:</b> you may provide <code>NULL</code> as argument for

  * <code>space</code>. Then this function will allocate the space and enforce

  * the #UCX_BUFFER_AUTOFREE flag.

  * 

  * @param space pointer to the memory area, or <code>NULL</code> to allocate

  * new memory

  * @param capacity the capacity of the buffer

  * @param flags buffer features (see UcxBuffer.flags)

  * @return the new buffer

  */

 UcxBuffer *ucx_buffer_new(void *space, size_t capacity, int flags);

 /**

  * Destroys a buffer.

  * 

  * If the #UCX_BUFFER_AUTOFREE feature is enabled, the contents of the buffer

  * are also freed.

  * 

  * @param buffer the buffer to destroy

  */

 void ucx_buffer_free(UcxBuffer* buffer);

 /**

  * Creates a new buffer and fills it with extracted content from another buffer.

  * 

  * <b>Note:</b> the #UCX_BUFFER_AUTOFREE feature is enforced for the new buffer.

  * 

  * @param src the source buffer

  * @param start the start position of extraction

  * @param length the count of bytes to extract (must not be zero)

  * @param flags feature mask for the new buffer

  * @return a new buffer containing the extraction

  */

 UcxBuffer* ucx_buffer_extract(UcxBuffer *src,

         size_t start, size_t length, int flags);

 /**

  * A shorthand macro for the full extraction of the buffer.

  * 

  * @param src the source buffer

  * @param flags feature mask for the new buffer

  * @return a new buffer with the extracted content

  */

 #define ucx_buffer_clone(src,flags) \

     ucx_buffer_extract(src, 0, (src)->capacity, flags)

 /**

  * Shifts the contents of the buffer by the given offset.

  * 

  * If the offset is positive, the contents are shifted to the right.

  * If auto extension is enabled, the buffer grows, if necessary.

  * In case the auto extension fails, this function returns a non-zero value and

  * no contents are changed.

  * If auto extension is disabled, the contents that do not fit into the buffer

  * are discarded.

  * 

  * If the offset is negative, the contents are shifted to the left where the

  * first <code>shift</code> bytes are discarded.

  * The new size of the buffer is the old size minus

  * the absolute shift value.

  * If this value is larger than the buffer size, the buffer is emptied (but

  * not cleared, see the security note below).

  * 

  * The buffer position gets shifted alongside with the content but is kept

  * within the boundaries of the buffer.

  * 

  * <b>Security note:</b> the shifting operation does <em>not</em> erase the

  * previously occupied memory cells. You can easily do that manually, e.g. by

  * calling <code>memset(buffer->space, 0, shift)</code> for a right shift or

  * <code>memset(buffer->size, 0, buffer->capacity-buffer->size)</code>

  * for a left shift.

  * 

  * @param buffer the buffer

  * @param shift the shift offset (negative means left shift)

  * @return 0 on success, non-zero if a required auto-extension fails

  */

 int ucx_buffer_shift(UcxBuffer* buffer, off_t shift);

 /**

  * Shifts the buffer to the right.

  * See ucx_buffer_shift() for details.

  * 

  * @param buffer the buffer

  * @param shift the shift offset

  * @return 0 on success, non-zero if a required auto-extension fails

  * @see ucx_buffer_shift()

  */

 int ucx_buffer_shift_right(UcxBuffer* buffer, size_t shift);

 /**

  * Shifts the buffer to the left.

  * 

  * See ucx_buffer_shift() for details. Note, however, that this method expects

  * a positive shift offset.

  * 

  * Since a left shift cannot fail due to memory allocation problems, this

  * function always returns zero.

  * 

  * @param buffer the buffer

  * @param shift the shift offset

  * @return always zero

  * @see ucx_buffer_shift()

  */

 int ucx_buffer_shift_left(UcxBuffer* buffer, size_t shift);

 /**

  * Moves the position of the buffer.

  * 

  * The new position is relative to the <code>whence</code> argument.

  *

  * SEEK_SET marks the start of the buffer.

  * SEEK_CUR marks the current position.

  * SEEK_END marks the end of the buffer.

  * 

  * With an offset of zero, this function sets the buffer position to zero

  * (SEEK_SET), the buffer size (SEEK_END) or leaves the buffer position

  * unchanged (SEEK_CUR).

  * 

  * @param buffer

  * @param offset position offset relative to <code>whence</code>

  * @param whence one of SEEK_SET, SEEK_CUR or SEEK_END

  * @return 0 on success, non-zero if the position is invalid

  *

  */

 int ucx_buffer_seek(UcxBuffer *buffer, off_t offset, int whence);

 /**

  * Clears the buffer by resetting the position and deleting the data.

  * 

  * The data is deleted by a zeroing it with call to <code>memset()</code>.

  * 

  * @param buffer the buffer to be cleared

  */

 #define ucx_buffer_clear(buffer) memset((buffer)->space, 0, (buffer)->size); \

         (buffer)->size = 0; (buffer)->pos = 0;

 /**

  * Tests, if the buffer position has exceeded the buffer capacity.

  * 

  * @param buffer the buffer to test

  * @return non-zero, if the current buffer position has exceeded the last

  * available byte of the buffer.

  */

 int ucx_buffer_eof(UcxBuffer *buffer);

 /**

  * Extends the capacity of the buffer.

  * 

  * <b>Note:</b> The buffer capacity increased by a power of two. I.e.

  * the buffer capacity is doubled, as long as it would not hold the current

  * content plus the additional required bytes.

  * 

  * <b>Attention:</b> the argument provided is the number of <i>additional</i>

  * bytes the buffer shall hold. It is <b>NOT</b> the total number of bytes the

  * buffer shall hold.

  * 

  * @param buffer the buffer to extend

  * @param additional_bytes the number of additional bytes the buffer shall

  * <i>at least</i> hold

  * @return 0 on success or a non-zero value on failure

  */

 int ucx_buffer_extend(UcxBuffer *buffer, size_t additional_bytes);

 /**

  * Writes data to a UcxBuffer.

  * 

  * The position of the buffer is increased by the number of bytes written.

  * 

  * @param ptr a pointer to the memory area containing the bytes to be written

  * @param size the length of one element

  * @param nitems the element count

  * @param buffer the UcxBuffer to write to

  * @return the total count of bytes written

  */

 size_t ucx_buffer_write(const void *ptr, size_t size, size_t nitems,

         UcxBuffer *buffer);

 /**

  * Reads data from a UcxBuffer.

  * 

  * The position of the buffer is increased by the number of bytes read.

  * 

  * @param ptr a pointer to the memory area where to store the read data

  * @param size the length of one element

  * @param nitems the element count

  * @param buffer the UcxBuffer to read from

  * @return the total number of elements read

  */

 size_t ucx_buffer_read(void *ptr, size_t size, size_t nitems,

         UcxBuffer *buffer);

 /**

  * Writes a character to a buffer.

  * 

  * The least significant byte of the argument is written to the buffer. If the

  * end of the buffer is reached and #UCX_BUFFER_AUTOEXTEND feature is enabled,

  * the buffer capacity is extended by ucx_buffer_extend(). If the feature is

  * disabled or buffer extension fails, <code>EOF</code> is returned.

  * 

  * On successful write the position of the buffer is increased.

  * 

  * @param buffer the buffer to write to

  * @param c the character to write as <code>int</code> value

  * @return the byte that has bean written as <code>int</code> value or

  * <code>EOF</code> when the end of the stream is reached and automatic

  * extension is not enabled or not possible

  */

 int ucx_buffer_putc(UcxBuffer *buffer, int c);

 /**

  * Gets a character from a buffer.

  * 

  * The current position of the buffer is increased after a successful read.

  * 

  * @param buffer the buffer to read from

  * @return the character as <code>int</code> value or <code>EOF</code>, if the

  * end of the buffer is reached

  */

 int ucx_buffer_getc(UcxBuffer *buffer);

 /**

  * Writes a string to a buffer.

  * 

  * @param buffer the buffer

  * @param str the string

  * @return the number of bytes written

  */

 size_t ucx_buffer_puts(UcxBuffer *buffer, const char *str);

 /**

  * Returns the complete buffer content as sstr_t.

  * @param buffer the buffer

  * @return the result of <code>sstrn()</code> with the buffer space and size

  * as arguments

  */

 #define ucx_buffer_to_sstr(buffer) sstrn((buffer)->space, (buffer)->size)

 #ifdef	__cplusplus

 }

 #endif

 #endif	/* UCX_BUFFER_H */