[Assorted-commits] SF.net SVN: assorted:[1138] sandbox/trunk/src/c

[<yan...@us...>]

Revision: 1138
          http://assorted.svn.sourceforge.net/assorted/?rev=1138&view=rev
Author:   yangzhang
Date:     2009-01-24 10:15:03 +0000 (Sat, 24 Jan 2009)

Log Message:
-----------
added more c sandbox items

Modified Paths:
--------------
    sandbox/trunk/src/c/switches.c

Added Paths:
-----------
    sandbox/trunk/src/c/arrayinit.c
    sandbox/trunk/src/c/coercion.mk
    sandbox/trunk/src/c/overflow/
    sandbox/trunk/src/c/rand.c
    sandbox/trunk/src/c/switchsyntax.c

Added: sandbox/trunk/src/c/arrayinit.c
===================================================================
--- sandbox/trunk/src/c/arrayinit.c	                        (rev 0)
+++ sandbox/trunk/src/c/arrayinit.c	2009-01-24 10:15:03 UTC (rev 1138)
@@ -0,0 +1,141 @@
+#include <stdio.h>
+
+// Array initialization syntax.
+
+int main() {
+  // Can be any order.
+  int xs[] = { [0] 0, [4] -4, [1] -1, [2] -2 };
+  printf("%d\n", xs[3]); // Garbage.
+  printf("%d\n", xs[4]); // As expected.
+  return 0;
+}
+
+#if 0
+/*
+ * Warning -- this file must be compiled with GCC
+ * to show the goto dispatching.  In particular,
+ * the compiler must be compatible with gnu99
+ * (i.e. -std=gnu99).
+ */
+
+/*
+ * Reminder -- disassemble with:
+ * objdump 4-jumptable -d > jumptable.asm
+ * Consider the generated asm.
+ */
+
+//enum simplifies unique numbers for opcodes
+enum {
+	OP_ADD = 0,
+	OP_SUB,
+	OP_MUL,
+	OP_DIV,
+	OP_MAX
+};
+
+int add(int x, int y);
+int sub(int x, int y);
+int mul(int x, int y);
+int div(int x, int y);
+int goto_dispatch(int op, int x, int y);
+
+int
+main(int argc, char **argv)
+{
+	void print_sw(int op, int r, int s) {
+		printf("SWCH: op %d (%d, %d) = %d\n", op, r, s, switch_dispatch(op, r, s));
+	}
+	print_sw(OP_ADD, 4, 5);
+	print_sw(OP_DIV, 8, 2);
+	switch_dispatch(7, 0, 0);
+	switch_dispatch(10, 0, 0);
+	switch_dispatch(15, 0, 0);
+	switch_dispatch(20, 0, 0);
+
+	//nested convenience function prints the op
+	void print_func(int op, int r, int s) {
+		printf("FUNC: op %d (%d, %d) = %d\n", op, r, s, func_dispatch(op, r, s));
+	};
+	//test a few dispatches
+	print_func(OP_ADD, 4, 5);
+	print_func(OP_DIV, 8, 2);
+
+	//what if we don't want to make a new stack frame?
+	void print_goto(int op, int r, int s) {
+		printf("GOTO: op %d (%d, %d) = %d\n", op, r, s, goto_dispatch(op, r, s));
+	}
+	print_goto(OP_ADD, 4, 5);
+	print_goto(OP_DIV, 8, 2);
+
+	return 0;
+}
+
+int
+switch_dispatch(int op, int x, int y)
+{
+	switch (op) {
+	case OP_ADD:
+		return x + y;
+	case OP_MUL:
+		return x * y;
+	case OP_DIV:
+		return x / y;
+	case OP_SUB:
+		return x - y;
+	case 7 ... 10:
+		printf("switch_dispatch invoked with opcode in range 7 to 10\n");
+		break;
+	case 15 ... 20:
+		printf("switch_dispatch invoked with opcode in range 15 to 20\n");
+		break;
+	}
+	return -1;
+}
+
+int
+func_dispatch(int op, int x, int y)
+{
+	//let's make a jumptable with function pointers
+	//compare with and without static
+	static int (*jumptable[OP_MAX])(int a, int b) = {
+		//named index notation lets us specify things out-of-order
+		[OP_ADD] add,
+		[OP_MUL] mul,
+		[OP_SUB] sub,
+		[OP_DIV] div
+	};
+	return jumptable[op](x, y);
+	//or
+	//return (*jumptable[op])(x, y);
+}
+
+int add(int x, int y) { return x + y; }
+int sub(int x, int y) { return x - y; }
+int mul(int x, int y) { return x * y; }
+int div(int x, int y) { return x / y; }
+
+int
+goto_dispatch(int op, int x, int y)
+{
+	//now, lets make a jumptable using gotos
+	static void *labeltable[OP_MAX] = {
+		//here we see the address-of-label syntax
+		[OP_ADD] &&l_add,
+		[OP_MUL] &&l_mul,
+		[OP_SUB] &&l_sub,
+		[OP_DIV] &&l_div
+	};
+
+	//we must dereference a label's address if we want to goto it
+	goto *labeltable[op];
+
+l_add:
+	return x+y;
+l_sub:
+	return x-y;
+l_mul:
+	return x*y;
+l_div:
+	return x/y;
+}
+#endif

Added: sandbox/trunk/src/c/coercion.mk
===================================================================
--- sandbox/trunk/src/c/coercion.mk	                        (rev 0)
+++ sandbox/trunk/src/c/coercion.mk	2009-01-24 10:15:03 UTC (rev 1138)
@@ -0,0 +1,2 @@
+coercion: coercion.c
+	gcc -Wconversion coercion.c

Added: sandbox/trunk/src/c/rand.c
===================================================================
--- sandbox/trunk/src/c/rand.c	                        (rev 0)
+++ sandbox/trunk/src/c/rand.c	2009-01-24 10:15:03 UTC (rev 1138)
@@ -0,0 +1,8 @@
+#include <limits.h>
+#include <stdlib.h>
+#include <stdio.h>
+int main() {
+  printf("RAND_MAX = %d\n", RAND_MAX);
+  printf("INT_MAX = %d\n", INT_MAX);
+  return 0;
+}

Modified: sandbox/trunk/src/c/switches.c
===================================================================
--- sandbox/trunk/src/c/switches.c	2009-01-23 21:44:55 UTC (rev 1137)
+++ sandbox/trunk/src/c/switches.c	2009-01-24 10:15:03 UTC (rev 1138)
@@ -1,4 +1,4 @@
-
+// Explore the generated asm code.
 int main() {
 	int x = 3;
 	switch (x) {

Added: sandbox/trunk/src/c/switchsyntax.c
===================================================================
--- sandbox/trunk/src/c/switchsyntax.c	                        (rev 0)
+++ sandbox/trunk/src/c/switchsyntax.c	2009-01-24 10:15:03 UTC (rev 1138)
@@ -0,0 +1,9 @@
+// Demo fancy switch range syntax.
+
+int main(int argc, char **argv) {
+  switch (argc) {
+    case 0 ... 3: return 0;
+    case 4 ... 8: return 1;
+    default:      return 2;
+  }
+}


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