foreach: new module

ccan/foreach/_info

+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * foreach - macro for simple iteration of arrays
+ *
+ * The foreach_int and foreach_ptr macros allow simple iteration of
+ * static arrays.  This is very efficient with good compiler support
+ * (ie. gcc), and not too bad (ie. a few compares and mallocs) for
+ * other compilers.
+ *
+ * License: LGPL (3 or any later version)
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ *
+ * Example:
+ *	// Figure out how to get usage: message out of a program.
+ *	#include <ccan/foreach/foreach.h>
+ *	#include <stdio.h>
+ *	#include <stdlib.h>
+ *	#include <string.h>
+ *	#include <err.h>
+ *
+ *	// Returns true if program outputs "usage:"
+ *	static bool try_usage(const char *prog, const char *arg)
+ *	{
+ *		char *command;
+ *		FILE *in;
+ *		int status;
+ *
+ *		command = malloc(strlen(prog) + 1 + strlen(arg) + 1 +
+ *				 sizeof("</dev/null 2>&1 | grep -qiw usage:"));
+ *		sprintf(command, "%s %s </dev/null 2>&1 | grep -qiw usage:",
+ *			prog, arg);
+ *		in = popen(command, "r");
+ *		if (!in)
+ *			err(2, "running '%s'", command);
+ *		status = pclose(in);
+ *		free(command);
+ *		return (WIFEXITED(status) && WEXITSTATUS(status) == 0);
+ *	}
+ *
+ *	int main(int argc, char *argv[])
+ *	{
+ *		const char *arg;
+ *
+ *		if (argc != 2)
+ *			errx(1, "Usage: %s <progname>\n"
+ *			     "Figures out how to get usage message", argv[0]);
+ *		foreach_ptr(arg, "--help", "-h", "--usage", "-?", "") {
+ *			if (try_usage(argv[1], arg)) {
+ *				printf("%s %s\n", argv[1], arg);
+ *				exit(0);
+ *			}
+ *		}
+ *		printf("%s is unhelpful\n", argv[1]);
+ *		exit(1);
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		return 0;
+	}
+
+	return 1;
+}

ccan/foreach/foreach.c

+#include <ccan/foreach/foreach.h>
+#include <ccan/list/list.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdarg.h>
+
+#if !HAVE_COMPOUND_LITERALS || !HAVE_FOR_LOOP_DECLARATION
+/* This list is normally very short. */
+static LIST_HEAD(iters);
+
+struct iter_info {
+	struct list_node list;
+	const void *index;
+	unsigned int i, num;
+};
+
+static void free_old_iters(const void *index)
+{
+	struct iter_info *i, *next;
+
+	list_for_each_safe(&iters, i, next, list) {
+		/* If we're re-using an index, free the old one.
+		 * Otherwise, if it's past i on the stack, it's old.  Don't
+		 * assume stack direction, but we know index is downstack. */
+		if (i->index == index
+		    || (((uintptr_t)index < (uintptr_t)&i)
+			== ((uintptr_t)&i < (uintptr_t)i->index))) {
+			list_del(&i->list);
+			free(i);
+		}
+	}
+}
+
+static struct iter_info *find_iter(const void *index)
+{
+	struct iter_info *i;
+
+	list_for_each(&iters, i, list) {
+		if (i->index == index)
+			return i;
+	}
+	abort();
+}
+
+static struct iter_info *new_iter(const void *index)
+{
+	struct iter_info *info = malloc(sizeof *info);
+	info->index = index;
+	info->i = info->num = 0;
+	list_add(&iters, &info->list);
+	return info;
+};
+
+#if HAVE_COMPOUND_LITERALS
+void _foreach_iter_init(const void *i)
+{
+	free_old_iters(i);
+	new_iter(i);
+}
+
+unsigned int _foreach_iter(const void *i)
+{
+	struct iter_info *info = find_iter(i);
+	return info->i;
+}
+
+unsigned int _foreach_iter_inc(const void *i)
+{
+	struct iter_info *info = find_iter(i);
+	return ++info->i;
+}
+#else /* Don't have compound literals... */
+int _foreach_term = 0x42430199;
+
+/* We count values at beginning, and every time around the loop.  We change
+ * the terminator each time, so we don't get fooled in case it really appears
+ * in the list. */
+static unsigned int count_vals(struct iter_info *info, va_list *ap)
+{
+	unsigned int i;
+	int val = 0;
+
+	for (i = 0; i < info->num || val != _foreach_term; i++) {
+		val = va_arg(*ap, int);
+	}
+	_foreach_term++;
+	return i;
+}
+
+int _foreach_intval_init(const void *i, int val, ...)
+{
+	va_list ap;
+	struct iter_info *info;
+
+	free_old_iters(i);
+	info = new_iter(i);
+
+	va_start(ap, val);
+	info->num = count_vals(info, &ap);
+	va_end(ap);
+
+	return val;
+}
+
+bool _foreach_intval_done(const void *i)
+{
+	struct iter_info *info = find_iter(i);
+	return info->i == info->num;
+}
+	
+int _foreach_intval_next(const void *i, int val, ...)
+{
+	struct iter_info *info = find_iter(i);
+	va_list ap;
+	unsigned int num;
+
+	va_start(ap, val);
+	info->num = count_vals(info, &ap);
+	va_end(ap);
+
+	info->i++;
+	assert(info->i <= info->num);
+	if (info->i == info->num)
+		return 0;
+
+	va_start(ap, val);
+	for (num = 0; num < info->i; num++)
+		val = va_arg(ap, int);
+
+	va_end(ap);
+	return val;
+}
+
+void *_foreach_ptrval_init(const void *i, const void *val, ...)
+{
+	struct iter_info *info;
+
+	free_old_iters(i);
+	info = new_iter(i);
+
+	return (void *)val;
+}
+
+void *_foreach_ptrval_next(const void *i, const void *val, ...)
+{
+	struct iter_info *info = find_iter(i);
+	va_list ap;
+	unsigned int num;
+
+	info->i++;
+	va_start(ap, val);
+	for (num = 0; num < info->i; num++)
+		val = va_arg(ap, void *);
+	va_end(ap);
+	return (void *)val;
+}
+#endif /* !HAVE_COMPOUND_LITERALS */
+#endif /* !HAVE_COMPOUND_LITERALS || !HAVE_FOR_LOOP_DECLARATION */

ccan/foreach/foreach.h

+#ifndef CCAN_FOREACH_H
+#define CCAN_FOREACH_H
+#include "config.h"
+#include <stddef.h>
+#include <assert.h>
+#include <stdbool.h>
+
+#if HAVE_COMPOUND_LITERALS
+#if HAVE_FOR_LOOP_DECLARATION
+/**
+ * foreach_int - iterate over a fixed series of integers
+ * @i: the int-compatible iteration variable
+ * @val: one or more integer-compatible values
+ *
+ * This is a convenient wrapper function for setting a variable to one or
+ * more explicit values in turn.  continue and break work as expected.
+ *
+ * Example:
+ *	int i;
+ *	foreach_int(i, 0, -1, 100, 0, -99) {
+ *		printf("i is %i\n", i);
+ *	}
+ */
+#define foreach_int(i, val, ...)					\
+	for (unsigned _foreach_i = ((i) = val, 0);			\
+	     _foreach_i < sizeof((int[]) { val, __VA_ARGS__ })/sizeof(val); \
+	     (i) = (int[]) { val, __VA_ARGS__, 0 }[++_foreach_i])
+
+/**
+ * foreach_ptr - iterate over a non-NULL series of pointers
+ * @i: the pointer iteration variable
+ * @val: one or more compatible pointer values
+ *
+ * This is a convenient wrapper function for setting a variable to one
+ * or more explicit values in turn.  None of the values can be NULL;
+ * that is the termination condition (ie. @i will be NULL on
+ * completion).  continue and break work as expected.
+ *
+ * Example:
+ *	const char *p;
+ *	foreach_ptr(p, "Hello", "world") {
+ *		printf("p is %s\n", p);
+ *	}
+ */
+#define foreach_ptr(i, val, ...)					\
+	for (unsigned _foreach_i = (unsigned long)((i) = (val), 0);	\
+	     (i);							\
+	     (i) = ((FOREACH_TYPEOF(val)[]){(val), __VA_ARGS__, NULL})	\
+		     [++_foreach_i])					\
+		_foreach_no_nullval(_foreach_i, i,			\
+				    ((void *[]){ val, __VA_ARGS__})))
+#else /* !HAVE_FOR_LOOP_DECLARATION */
+/* GCC in C89 mode still has compound literals, but no for-declarations */
+#define foreach_int(i, val, ...)					\
+	for ((i) = (val), _foreach_iter_init(&(i));			\
+	     _foreach_iter(&(i)) < sizeof((int[]) { (val), __VA_ARGS__ }) \
+			   / sizeof(int);				\
+	     (i) = (int[]) { (val), __VA_ARGS__, 0 }[_foreach_iter_inc(&(i))])
+
+#define foreach_ptr(i, val, ...)					\
+	for ((i) = (val), _foreach_iter_init(&(i));			\
+	     (i);							\
+	     (i) = ((FOREACH_TYPEOF(val)[]){ (val), __VA_ARGS__, 0 })	\
+		     [_foreach_iter_inc(&(i))],				\
+		 _foreach_no_nullval(_foreach_iter(&(i)), i,		\
+				     ((void *[]){ val, __VA_ARGS__})))
+
+void _foreach_iter_init(const void *i);
+unsigned int _foreach_iter(const void *i);
+unsigned int _foreach_iter_inc(const void *i);
+
+#endif /* !HAVE_FOR_LOOP_DECLARATION */
+
+/* Make sure they don't put NULL values into array! */
+#define _foreach_no_nullval(i, p, arr)				\
+	assert((i) >= sizeof(arr)/sizeof(arr[0]) || (p))
+
+#if HAVE_TYPEOF
+#define FOREACH_TYPEOF(val) __typeof__(&*(val))
+#else
+#define FOREACH_TYPEOF(val) void *
+#endif
+
+#else /* !HAVE_COMPOUND_LITERALS */
+
+/* No compound literals, but it's still (just) possible. */
+#define foreach_int(i, val, ...)					\
+	for (i = _foreach_intval_init(&(i), val, __VA_ARGS__,	\
+					  _foreach_term);		\
+	     !_foreach_intval_done(&i);				\
+	     i = _foreach_intval_next(&(i), val, __VA_ARGS__,	\
+					  _foreach_term))
+
+#define foreach_ptr(i, val, ...)					\
+	for (i = _foreach_ptrval_init(&(i), val, __VA_ARGS__, NULL);	\
+	     (i);							\
+	     i = _foreach_ptrval_next(&(i), val, __VA_ARGS__, NULL))
+
+extern int _foreach_term;
+int _foreach_intval_init(const void *i, int val, ...);
+bool _foreach_intval_done(const void *i);
+int _foreach_intval_next(const void *i, int val, ...);
+void *_foreach_ptrval_init(const void *i, const void *val, ...);
+void *_foreach_ptrval_next(const void *i, const void *val, ...);
+#endif /* !HAVE_COMPOUND_LITERALS */
+
+#endif /* CCAN_FOREACH_H */

ccan/foreach/test/run-break.c

+#include <ccan/foreach/foreach.h>
+#include <ccan/tap/tap.h>
+#include <stdio.h>
+#include <string.h>
+#include <ccan/foreach/foreach.c>
+
+static int count_iters(void)
+{
+	unsigned int count = 0;
+#if !HAVE_COMPOUND_LITERALS || !HAVE_FOR_LOOP_DECLARATION
+	struct iter_info *i;
+	
+	list_for_each(&iters, i, list)
+		count++;
+#endif
+	return count;
+}
+
+int main(void)
+{
+	int i, j, sum;
+
+	plan_tests(2);
+
+	sum = 0;
+	foreach_int(i, 0, 1, 2, 3, 4) {
+		foreach_int(j, 0, 1, 2, 3, 4) {
+			sum += i*j;
+			if (j == i)
+				break;
+		}
+	}
+	ok1(sum == 65);
+	ok1(count_iters() <= 2);
+
+	return exit_status();
+}
+       

ccan/foreach/test/run-nested.c

+#include <ccan/foreach/foreach.h>
+#include <ccan/tap/tap.h>
+#include <stdio.h>
+#include <string.h>
+#include <ccan/foreach/foreach.c>
+
+static int test_int_recursion(unsigned int level)
+{
+	int i, sum = 0;
+
+	foreach_int(i, 0, 1, 2, 3, 4) {
+		sum += i;
+		if (i > level)
+			sum += test_int_recursion(i);
+	}
+	return sum;
+}
+
+static int test_ptr_recursion(const char *level)
+{
+	int sum = 0;
+	const char *i;
+
+	foreach_ptr(i, "0", "1", "2", "3", "4") {
+		sum += atoi(i);
+		if (atoi(i) > atoi(level))
+			sum += test_ptr_recursion(i);
+	}
+	return sum;
+}
+
+static int count_iters(void)
+{
+	unsigned int count = 0;
+#if !HAVE_COMPOUND_LITERALS || !HAVE_FOR_LOOP_DECLARATION
+	struct iter_info *i;
+	
+	list_for_each(&iters, i, list)
+		count++;
+#endif
+	return count;
+}
+
+int main(void)
+{
+	int i, j, sum;
+	const char *istr, *jstr;
+
+	plan_tests(12);
+
+	sum = 0;
+	foreach_int(i, 0, 1, 2, 3, 4)
+		foreach_int(j, 0, 1, 2, 3, 4)
+			sum += i*j;
+	diag("sum = %i\n", sum);
+	diag("iters = %i\n", count_iters());
+	ok1(sum == 100);
+	ok1(count_iters() <= 2);
+
+	/* Same again... reusing iterators. */
+	sum = 0;
+	foreach_int(i, 0, 1, 2, 3, 4)
+		foreach_int(j, 0, 1, 2, 3, 4)
+			sum += i*j;
+	diag("sum = %i\n", sum);
+	diag("iters = %i\n", count_iters());
+	ok1(sum == 100);
+	ok1(count_iters() <= 2);
+
+	sum = test_int_recursion(0);
+	diag("sum = %i\n", sum);
+	diag("iters = %i\n", count_iters());
+	ok1(sum == 160);
+	ok1(count_iters() <= 2 + 5); /* 5 is max depth of recursion. */
+
+	sum = 0;
+	foreach_ptr(istr, "0", "1", "2", "3", "4")
+		foreach_ptr(jstr, "0", "1", "2", "3", "4")
+			sum += atoi(istr)*atoi(jstr);
+	diag("sum = %i\n", sum);
+	diag("iters = %i\n", count_iters());
+	ok1(sum == 100);
+	ok1(count_iters() <= 2 + 5 + 2);
+
+	/* Same again... reusing iterators. */
+	sum = 0;
+	foreach_ptr(istr, "0", "1", "2", "3", "4")
+		foreach_ptr(jstr, "0", "1", "2", "3", "4")
+			sum += atoi(istr)*atoi(jstr);
+	diag("sum = %i\n", sum);
+	diag("iters = %i\n", count_iters());
+	ok1(sum == 100);
+	ok1(count_iters() <= 2 + 5 + 2);
+
+	sum = test_ptr_recursion("0");
+	diag("sum = %i\n", sum);
+	diag("iters = %i\n", count_iters());
+	ok1(sum == 160);
+	ok1(count_iters() <= 2 + 5 + 2);
+	return exit_status();
+}
+       

ccan/foreach/test/run.c

+#include <ccan/foreach/foreach.h>
+#include <ccan/tap/tap.h>
+#include <stdio.h>
+#include <string.h>
+#include <ccan/foreach/foreach.c>
+
+int main(void)
+{
+	int i, expecti;
+	const char *p, *expectp[] = { "hello", "there", "big", "big", "world" };
+
+	plan_tests(11);
+
+	expecti = 0;
+	foreach_int(i, 0, 1, 2, 3, 4) {
+		ok1(i == expecti);
+		expecti++;
+	}
+
+	expecti = 0;
+	foreach_ptr(p, "hello", "there", "big", "big", "world") {
+		ok1(strcmp(expectp[expecti], p) == 0);
+		expecti++;
+	}
+	ok1(p == NULL);
+
+	return exit_status();
+}
+       

config.h

@@ -18,6 +18,8 @@
 #define HAVE_BUILTIN_POPCOUNTL 1
 #define HAVE_BUILTIN_TYPES_COMPATIBLE_P 1
 #define HAVE_BYTESWAP_H 1
+#define HAVE_COMPOUND_LITERALS 1
+#define HAVE_FOR_LOOP_DECLARATION 0
 #define HAVE_GETPAGESIZE 1
 #define HAVE_LITTLE_ENDIAN 1
 #define HAVE_MMAP 1