1 files changed, 51 insertions, 0 deletions
diff --git a/src/instruction/reverse.c b/src/instruction/reverse.c
new file mode 100644
index 0000000..bd863ae
--- /dev/null
+++ b/src/instruction/reverse.c
@@ -0,0 +1,51 @@
+#include "3cl.h"
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "readchar.h"
+#include "utils.h"
+#include "variable.h"
+
+
+struct CCLFrame *ccl_instruction_reverse(struct CCL *ccl, struct CCLFrame *frame)
+{
+    char varname;
+    size_t toreverse;
+
+    varname = ccl_readchar(ccl, frame, CCL_RC_CCL_VARUS);
+    if (varname == '\0')
+    {
+        die(1, "Unexpected EOF");
+    } else if (varname == '_')
+    {
+        toreverse = ccl->stack.cur;
+    } else
+    {
+        struct CCLVariable *var = ccl_variable_getany(ccl, frame, varname);
+        if (var == NULL)
+            die(1, "Unknown variable '%c' at %d", varname, frame->ep);
+        toreverse = var->value;
+    }
+
+    if (ccl->stack.cur < toreverse)
+        die(1, "stack size is %d (%d required)", ccl->stack.cur, toreverse);
+
+    CCLNum *temp = malloc(sizeof(*temp) * toreverse);
+    if (temp == NULL)
+        die(1, "malloc(): %s", strerror(errno));
+
+    size_t start;
+    for (start = 0; start < toreverse; ++start)
+        temp[start] = ccl->stack.stack[ccl->stack.cur - start];
+    start = ccl->stack.cur - start;
+    for (int i = 0; i < toreverse; ++i)
+        ccl->stack.stack[start + i] = temp[i];
+
+    free(temp);
+
+    return frame;
+}