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git-svn-id: svn://svn.cc65.org/cc65/trunk@3 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/common/malloc.c

@@ -0,0 +1,125 @@
+/*
+ * malloc.c
+ *
+ * Ullrich von Bassewitz, 03.06.1998
+ */
+
+
+
+#include <stddef.h>
+#include "_heap.h"
+
+
+
+void* malloc (size_t size)
+/* Allocate memory from the given heap. The function returns a pointer to the
+ * allocated memory block or a NULL pointer if not enough memory is available.
+ * Allocating a zero size block is not allowed.
+ */
+{
+    struct freeblock* f;
+    unsigned* p;
+
+
+    /* Check for a size of zero, then add the administration space and round
+     * up the size if needed.
+     */
+    if (size == 0) {
+	return 0;
+    }
+    size += HEAP_ADMIN_SPACE;
+    if (size < sizeof (struct freeblock)) {
+        size = sizeof (struct freeblock);
+    }
+
+    /* Search the freelist for a block that is big enough */
+    f = _hfirst;
+    while (f && f->size < size) {
+        f = f->next;
+    }
+
+    /* Did we find one? */
+    if (f) {
+
+        /* We found a block big enough. If the block can hold just the
+         * requested size, use the block in full. Beware: When slicing blocks,
+         * there must be space enough to create a new one! If this is not the
+         * case, then use the complete block.
+         */
+        if (f->size - size < sizeof (struct freeblock)) {
+
+            /* Use the actual size */
+            size = f->size;
+
+            /* Remove the block from the free list */
+            if (f->prev) {
+                /* We have a previous block */
+                f->prev->next = f->next;
+            } else {
+                /* This is the first block, correct the freelist pointer */
+                _hfirst = f->next;
+            }
+            if (f->next) {
+                /* We have a next block */
+                f->next->prev = f->prev;
+            } else {
+                /* This is the last block, correct the freelist pointer */
+                _hlast = f->prev;
+            }
+
+        } else {
+
+            /* We must slice the block found */
+            struct freeblock* newblock;
+       	    newblock = (struct freeblock*) ((unsigned) f) + size;
+
+            /* Insert the new block (the remaining space) instead of the
+             * old one.
+             */
+            newblock->size = f->size - size;         /* Remaining size */
+            newblock->next = f->next;
+            newblock->prev = f->prev;
+            if (f->prev) {
+                /* We have a previous block */
+                f->prev->next = newblock;
+            } else {
+                /* This is the first block, correct the freelist pointer */
+                _hfirst = newblock;
+            }
+            if (f->next) {
+                /* We have a next block */
+                f->next->prev = newblock;
+            } else {
+                /* This is the last block, correct the freelist pointer */
+                _hlast = newblock;
+            }
+
+        }
+
+        /* Setup the pointer for the bock */
+        p = (unsigned*) f;
+
+    } else {
+
+        /* We did not find a block big enough. Try to use new space from the
+         * heap top.
+         */
+	if (((unsigned) _hend) - ((unsigned) _hptr) < size) {
+            /* Out of heap space */
+            return 0;
+    	}
+
+
+	/* There is enough space left, take it from the heap top */
+	p = _hptr;
+       	_hptr = (unsigned*) (((unsigned) _hptr) + size);
+
+    }
+
+    /* New block is now in p. Fill in the size and return the user pointer */
+    *p++ = size;
+    return p;
+}
+
+
+