diff -r 809581724cc7 -r 0358f1d9c506 ucx/buffer.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ucx/buffer.c	Mon May 22 16:17:26 2023 +0200
@@ -0,0 +1,415 @@
+/*
+ * 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 <stdio.h>
+#include <string.h>
+
+int cxBufferInit(
+        CxBuffer *buffer,
+        void *space,
+        size_t capacity,
+        CxAllocator const *allocator,
+        int flags
+) {
+    if (allocator == NULL) allocator = cxDefaultAllocator;
+    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);
+    }
+}
+
+CxBuffer *cxBufferCreate(
+        void *space,
+        size_t capacity,
+        CxAllocator const *allocator,
+        int flags
+) {
+    CxBuffer *buf = cxMalloc(allocator, sizeof(CxBuffer));
+    if (buf == NULL) return NULL;
+    if (0 == cxBufferInit(buf, space, capacity, allocator, flags)) {
+        return buf;
+    } else {
+        cxFree(allocator, buf);
+        return NULL;
+    }
+}
+
+void cxBufferFree(CxBuffer *buffer) {
+    if ((buffer->flags & CX_BUFFER_FREE_CONTENTS) == CX_BUFFER_FREE_CONTENTS) {
+        cxFree(buffer->allocator, buffer->bytes);
+    }
+    cxFree(buffer->allocator, buffer);
+}
+
+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;
+                // report the directly flushed items as written plus the remaining stuff
+                return items_flush + 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 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;
+    }
+}