diff -r 99a34860c105 -r d938228c382e src/ucx/cx/buffer.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/ucx/cx/buffer.h	Sun Nov 06 15:53:32 2022 +0100
@@ -0,0 +1,414 @@
+/*
+ * 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 "allocator.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;
+    };
+    /** The allocator to use for automatic memory management. */
+    CxAllocator const *allocator;
+    /** 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;
+    /**
+     * The buffer may not extend beyond this threshold before starting to flush.
+     * Default is \c SIZE_MAX (flushing disabled when auto extension is enabled).
+     */
+    size_t flush_threshold;
+    /**
+     * The block size for the elements to flush.
+     * Default is 4096 bytes.
+     */
+    size_t flush_blksize;
+    /**
+     * The maximum number of blocks to flush in one cycle.
+     * Zero disables flushing entirely (this is the default).
+     * Set this to \c SIZE_MAX to flush the entire buffer.
+     *
+     * @attention if the maximum number of blocks multiplied with the block size
+     * is smaller than the expected contents written to this buffer within one write
+     * operation, multiple flush cycles are performed after that write.
+     * That means the total number of blocks flushed after one write to this buffer may
+     * be larger than \c flush_blkmax.
+     */
+    size_t flush_blkmax;
+
+    /**
+     * The write function used for flushing.
+     * If NULL, the flushed content gets discarded.
+     */
+    cx_write_func flush_func;
+
+    /**
+     * The target for \c flush_func.
+     */
+    void *flush_target;
+
+    /**
+     * 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;
+
+/**
+ * Initializes a fresh 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 buffer the buffer to initialize
+ * @param space pointer to the memory area, or \c NULL to allocate
+ * new memory
+ * @param capacity the capacity of the buffer
+ * @param allocator the allocator this buffer shall use for automatic memory management
+ * @param flags buffer features (see cx_buffer_s.flags)
+ * @return zero on success, non-zero if a required allocation failed
+ */
+__attribute__((__nonnull__(1, 4)))
+int cxBufferInit(
+        CxBuffer *buffer,
+        void *space,
+        size_t capacity,
+        CxAllocator const *allocator,
+        int flags
+);
+
+/**
+ * Destroys the buffer contents.
+ *
+ * Has no effect if the #CX_BUFFER_FREE_CONTENTS feature is not enabled.
+ *
+ * @param buffer the buffer which contents shall be destroyed
+ */
+__attribute__((__nonnull__))
+void cxBufferDestroy(CxBuffer *buffer);
+
+/**
+ * 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.
+ *
+ * \attention
+ * Security Note: The shifting operation does \em not erase the previously occupied memory cells.
+ * But 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->bytes + 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
+ */
+__attribute__((__nonnull__))
+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()
+ */
+__attribute__((__nonnull__))
+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()
+ */
+__attribute__((__nonnull__))
+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
+ *
+ */
+__attribute__((__nonnull__))
+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
+ */
+__attribute__((__nonnull__))
+void cxBufferClear(CxBuffer *buffer);
+
+/**
+ * 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.
+ */
+__attribute__((__nonnull__))
+int cxBufferEof(CxBuffer const *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
+ */
+__attribute__((__nonnull__))
+int cxBufferMinimumCapacity(
+        CxBuffer *buffer,
+        size_t capacity
+);
+
+/**
+ * Writes data to a CxBuffer.
+ *
+ * If flushing is enabled and the buffer needs to flush, the data is flushed to
+ * the target until the target signals that it cannot take more data by
+ * returning zero via the respective write function. In that case, the remaining
+ * data in this buffer is shifted to the beginning of this buffer so that the
+ * newly available space can be used to append as much data as possible. This
+ * function only stops writing more elements, when the flush target and this
+ * buffer are both incapable of taking more data or all data has been written.
+ * The number returned by this function is the total number of elements that
+ * could be written during the process. It does not necessarily mean that those
+ * elements are still in this buffer, because some of them could have also be
+ * flushed already.
+ *
+ * If automatic flushing is not enabled, 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 elements written
+ */
+__attribute__((__nonnull__))
+size_t cxBufferWrite(
+        void const *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
+ */
+__attribute__((__nonnull__))
+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
+ */
+__attribute__((__nonnull__))
+int cxBufferPut(
+        CxBuffer *buffer,
+        int c
+);
+
+/**
+ * Writes a string to a buffer.
+ *
+ * @param buffer the buffer
+ * @param str the zero-terminated string
+ * @return the number of bytes written
+ */
+__attribute__((__nonnull__))
+size_t cxBufferPutString(
+        CxBuffer *buffer,
+        const char *str
+);
+
+/**
+ * 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
+ */
+__attribute__((__nonnull__))
+int cxBufferGet(CxBuffer *buffer);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* UCX_BUFFER_H */