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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.

  */

 /**

  * \file buffer.h

  *

  * \brief Advanced buffer implementation.

  *

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

  * would do with a stream.

  *

  * 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

  * \version 3.0

  * \copyright 2-Clause BSD License

  */

 #ifndef UCX_BUFFER_H

 #define UCX_BUFFER_H

 #include "common.h"

 #include <stdio.h>

 #ifdef    __cplusplus

 extern "C" {

 #endif

 /**

  * No buffer features enabled (all flags cleared).

  */

 #define CX_BUFFER_DEFAULT 0x00

 /**

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

  */

 #define CX_BUFFER_FREE_CONTENTS 0x01

 /**

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

  */

 #define CX_BUFFER_AUTO_EXTEND 0x02

 /** Structure for the UCX buffer data. */

 typedef struct {

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

     union {

         /**

          * Data is interpreted as text.

          */

         char *space;

         /**

          * Data is interpreted as binary.

          */

         unsigned char *bytes;

     };

     /** 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 #CX_BUFFER_DEFAULT

      * \see #CX_BUFFER_FREE_CONTENTS

      * \see #CX_BUFFER_AUTO_EXTEND

      */

     int flags;

 } cx_buffer_s;

 /**

  * UCX buffer.

  */

 typedef cx_buffer_s *CxBuffer;

 /**

  * Creates a new buffer.

  *

  * \note You may provide \c NULL as argument for \p space.

  * Then this function will allocate the space and enforce

  * the #CX_BUFFER_FREE_CONTENTS 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 cx_buffer_s.flags)

  * \return the new buffer

  */

 CxBuffer cxBufferCreate(

         void *space,

         size_t capacity,

         int flags

 );

 /**

  * Destroys a buffer.

  *

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

  * are also freed.

  *

  * \param buffer the buffer to destroy

  */

 void cxBufferDestroy(CxBuffer buffer);

 /**

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

  *

  * \note The #CX_BUFFER_FREE_CONTENTS 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 features for the new buffer (#CX_BUFFER_FREE_CONTENTS will always be enabled)

  * \return a new buffer containing the extraction

  */

 CxBuffer cxBufferExtract(

         CxBuffer src,

         size_t start,

         size_t length,

         int flags

 );

 /**

  * A shorthand macro for copying an entire buffer.

  *

  * \param src the source buffer

  * \param flags features for the new buffer (#CX_BUFFER_FREE_CONTENTS will always be enabled)

  * \return a new buffer with the copied content

  */

 #define cxBufferClone(src, flags) cxBufferExtract(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 \p shift 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.

  *

  * \note For situations where \c off_t is not large enough, there are specialized cxBufferShiftLeft() and

  * cxBufferShiftRight() functions using a \c size_t as parameter type.

  *

  * \par Security Note

  * The shifting operation does \em not erase the previously occupied memory cells.

  * You can easily do that manually, e.g. by calling

  * <code>memset(buffer->bytes, 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 cxBufferShift(

         CxBuffer buffer,

         off_t shift

 );

 /**

  * Shifts the buffer to the right.

  * See cxBufferShift() for details.

  *

  * \param buffer the buffer

  * \param shift the shift offset

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

  * \see cxBufferShift()

  */

 int cxBufferShiftRight(

         CxBuffer buffer,

         size_t shift

 );

 /**

  * Shifts the buffer to the left.

  * See cxBufferShift() for details.

  *

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

  * function always returns zero.

  *

  * \param buffer the buffer

  * \param shift the positive shift offset

  * \return always zero

  * \see cxBufferShift()

  */

 int cxBufferShiftLeft(

         CxBuffer buffer,

         size_t shift

 );

 /**

  * Moves the position of the buffer.

  *

  * The new position is relative to the \p whence argument.

  *

  * \li \c SEEK_SET marks the start of the buffer.

  * \li \c SEEK_CUR marks the current position.

  * \li \c SEEK_END marks the end of the buffer.

  *

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

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

  * unchanged (\c SEEK_CUR).

  *

  * \param buffer the buffer

  * \param offset position offset relative to \p whence

  * \param whence one of \c SEEK_SET, \c SEEK_CUR or \c SEEK_END

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

  *

  */

 int cxBufferSeek(

         CxBuffer buffer,

         off_t offset,

         int whence

 );

 /**

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

  *

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

  *

  * \param buffer the buffer to be cleared

  */

 #define cxBufferClear(buffer) memset((buffer)->bytes, 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 cxBufferEof(CxBuffer buffer);

 /**

  * Ensures that the buffer has a minimum capacity.

  *

  * If the current capacity is not sufficient, the buffer will be extended.

  *

  * \param buffer the buffer

  * \param capacity the minimum required capacity for this buffer

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

  */

 int cxBufferMinimumCapacity(

         CxBuffer buffer,

         size_t capacity

 );

 /**

  * Writes data to a CxBuffer.

  *

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

  *

  * \note The signature is compatible with the fwrite() family of functions.

  *

  * \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 CxBuffer to write to

  * \return the total count of bytes written

  */

 size_t cxBufferWrite(

         const void *ptr,

         size_t size,

         size_t nitems,

         CxBuffer buffer

 );

 /**

  * Reads data from a CxBuffer.

  *

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

  *

  * \note The signature is compatible with the fread() family of functions.

  *

  * \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 CxBuffer to read from

  * \return the total number of elements read

  */

 size_t cxBufferRead(

         void *ptr,

         size_t size,

         size_t nitems,

         CxBuffer 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 #CX_BUFFER_AUTO_EXTEND feature is enabled,

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

  * disabled or buffer extension fails, \c EOF 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

  * \return the byte that has bean written or \c EOF when the end of the stream is

  * reached and automatic extension is not enabled or not possible

  */

 int cxBufferPut(

         CxBuffer 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 or \c EOF, if the end of the buffer is reached

  */

 int cxBufferGet(CxBuffer buffer);

 /**

  * Writes a string to a buffer.

  *

  * \param buffer the buffer

  * \param str the zero-terminated string

  * \return the number of bytes written

  */

 size_t cxBufferPutString(

         CxBuffer buffer,

         const char *str

 );

 #ifdef __cplusplus

 }

 #endif

 #endif /* UCX_BUFFER_H */