Endianness module.

ccan/endian/_info.c

+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * endian - endian conversion macros for simple types
+ *
+ * Portable protocols (such as on-disk formats, or network protocols)
+ * are often defined to be a particular endian: little-endian (least
+ * significant bytes first) or big-endian (most significant bytes
+ * first).
+ *
+ * Similarly, some CPUs lay out values in memory in little-endian
+ * order (most commonly, Intel's 8086 and derivatives), or big-endian
+ * order (almost everyone else).
+ *
+ * This module provides conversion routines, inspired by the linux kernel.
+ *
+ * Example:
+ *	#include <stdio.h>
+ *	#include <err.h>
+ *	#include <ccan/endian/endian.h>
+ *
+ *	// 
+ *	int main(int argc, char *argv[])
+ *	{
+ *		uint32_t value;
+ *
+ *		if (argc != 2)
+ *			errx(1, "Usage: %s <value>", argv[0]);
+ *
+ *		printf("native:        %08x\n", value);
+ *		printf("little-endian: %08x\n", cpu_to_le32(value));
+ *		printf("big-endian:    %08x\n", cpu_to_be32(value));
+ *		printf("byte-reversed: %08x\n", swab_u32(value));
+ *		exit(0);
+ *	}
+ *
+ * Licence: LGPL (2 or any later version)
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0)
+		/* Nothing */
+		return 0;
+
+	return 1;
+}

ccan/endian/endian.h

+#ifndef CCAN_ENDIAN_H
+#define CCAN_ENDIAN_H
+#include <stdint.h>
+#include "config.h"
+
+/**
+ * swab_u16 - reverse bytes in a uint16_t value.
+ * @val: value whose bytes to swap.
+ */
+static inline uint16_t swab_u16(uint16_t val)
+{
+	return ((val & (uint16_t)0x00ffU) << 8)
+		| ((val & (uint16_t)0xff00U) >> 8);
+}
+
+/**
+ * swab_u32 - reverse bytes in a uint32_t value.
+ * @val: value whose bytes to swap.
+ */
+static inline uint32_t swab_u32(uint32_t val)
+{
+	return ((val & (uint32_t)0x000000ffUL) << 24)
+		| ((val & (uint32_t)0x0000ff00UL) <<  8)
+		| ((val & (uint32_t)0x00ff0000UL) >>  8) 
+		| ((val & (uint32_t)0xff000000UL) >> 24);
+}
+
+/**
+ * swab_u64 - reverse bytes in a uint64_t value.
+ * @val: value whose bytes to swap.
+ */
+static inline uint64_t swab_u64(uint64_t val)
+{
+	return ((val & (uint64_t)0x00000000000000ffULL) << 56)
+		| ((val & (uint64_t)0x000000000000ff00ULL) << 40)
+		| ((val & (uint64_t)0x0000000000ff0000ULL) << 24)
+		| ((val & (uint64_t)0x00000000ff000000ULL) <<  8)
+		| ((val & (uint64_t)0x000000ff00000000ULL) >>  8)
+		| ((val & (uint64_t)0x0000ff0000000000ULL) >> 24)
+		| ((val & (uint64_t)0x00ff000000000000ULL) >> 40)
+		| ((val & (uint64_t)0xff00000000000000ULL) >> 56);
+}
+
+/* Sanity check the defines.  We don't handle weird endianness. */
+#if !HAVE_LITTLE_ENDIAN && !HAVE_BIG_ENDIAN
+#error "Unknown endian"
+#elif HAVE_LITTLE_ENDIAN && HAVE_BIG_ENDIAN
+#error "Can't compile for both big and little endian."
+#endif
+
+/**
+ * cpu_to_le64 - convert a uint64_t value to little-endian
+ * @native: value to convert
+ */
+static inline uint64_t cpu_to_le64(uint64_t native)
+{
+#if HAVE_LITTLE_ENDIAN
+	return native;
+#else
+	return swab_u64(native);
+#endif
+}
+
+/**
+ * cpu_to_le32 - convert a uint32_t value to little-endian
+ * @native: value to convert
+ */
+static inline uint32_t cpu_to_le32(uint32_t native)
+{
+#if HAVE_LITTLE_ENDIAN
+	return native;
+#else
+	return swab_u32(native);
+#endif
+}
+
+/**
+ * cpu_to_le16 - convert a uint16_t value to little-endian
+ * @native: value to convert
+ */
+static inline uint16_t cpu_to_le16(uint16_t native)
+{
+#if HAVE_LITTLE_ENDIAN
+	return native;
+#else
+	return swab_u16(native);
+#endif
+}
+
+/**
+ * le64_to_cpu - convert a little-endian uint64_t value
+ * @le_val: little-endian value to convert
+ */
+static inline uint64_t le64_to_cpu(uint64_t le_val)
+{
+#if HAVE_LITTLE_ENDIAN
+	return le_val;
+#else
+	return swab_u64(le_val);
+#endif
+}
+
+/**
+ * le32_to_cpu - convert a little-endian uint32_t value
+ * @le_val: little-endian value to convert
+ */
+static inline uint32_t le32_to_cpu(uint32_t le_val)
+{
+#if HAVE_LITTLE_ENDIAN
+	return le_val;
+#else
+	return swab_u32(le_val);
+#endif
+}
+
+/**
+ * le16_to_cpu - convert a little-endian uint16_t value
+ * @le_val: little-endian value to convert
+ */
+static inline uint16_t le16_to_cpu(uint16_t le_val)
+{
+#if HAVE_LITTLE_ENDIAN
+	return le_val;
+#else
+	return swab_u16(le_val);
+#endif
+}
+
+/**
+ * cpu_to_be64 - convert a uint64_t value to big endian.
+ * @native: value to convert
+ */
+static inline uint64_t cpu_to_be64(uint64_t native)
+{
+#if HAVE_LITTLE_ENDIAN
+	return swab_u64(native);
+#else
+	return native;
+#endif
+}
+
+/**
+ * cpu_to_be32 - convert a uint32_t value to big endian.
+ * @native: value to convert
+ */
+static inline uint32_t cpu_to_be32(uint32_t native)
+{
+#if HAVE_LITTLE_ENDIAN
+	return swab_u32(native);
+#else
+	return native;
+#endif
+}
+
+/**
+ * cpu_to_be16 - convert a uint16_t value to big endian.
+ * @native: value to convert
+ */
+static inline uint16_t cpu_to_be16(uint16_t native)
+{
+#if HAVE_LITTLE_ENDIAN
+	return swab_u16(native);
+#else
+	return native;
+#endif
+}
+
+/**
+ * be64_to_cpu - convert a big-endian uint64_t value
+ * @be_val: big-endian value to convert
+ */
+static inline uint64_t be64_to_cpu(uint64_t be_val)
+{
+#if HAVE_LITTLE_ENDIAN
+	return swab_u64(be_val);
+#else
+	return be_val;
+#endif
+}
+
+/**
+ * be32_to_cpu - convert a big-endian uint32_t value
+ * @be_val: big-endian value to convert
+ */
+static inline uint32_t be32_to_cpu(uint32_t be_val)
+{
+#if HAVE_LITTLE_ENDIAN
+	return swab_u32(be_val);
+#else
+	return be_val;
+#endif
+}
+
+/**
+ * be16_to_cpu - convert a big-endian uint16_t value
+ * @be_val: big-endian value to convert
+ */
+static inline uint16_t be16_to_cpu(uint16_t be_val)
+{
+#if HAVE_LITTLE_ENDIAN
+	return swab_u16(be_val);
+#else
+	return be_val;
+#endif
+}
+
+#endif /* CCAN_ENDIAN_H */

ccan/endian/test/run.c

+#include <stdlib.h>
+#include <stddef.h>
+#include <tap/tap.h>
+#include "endian/endian.h"
+
+int main(int argc, char *argv[])
+{
+	union {
+		uint64_t u64;
+		unsigned char u64_bytes[8];
+	} u64;
+	union {
+		uint32_t u32;
+		unsigned char u32_bytes[4];
+	} u32;
+	union {
+		uint16_t u16;
+		unsigned char u16_bytes[2];
+	} u16;
+
+	plan_tests(48);
+
+	/* Straight swap tests. */
+	u64.u64_bytes[0] = 0x00;
+	u64.u64_bytes[1] = 0x11;
+	u64.u64_bytes[2] = 0x22;
+	u64.u64_bytes[3] = 0x33;
+	u64.u64_bytes[4] = 0x44;
+	u64.u64_bytes[5] = 0x55;
+	u64.u64_bytes[6] = 0x66;
+	u64.u64_bytes[7] = 0x77;
+	u64.u64 = swab_u64(u64.u64);
+	ok1(u64.u64_bytes[7] == 0x00);
+	ok1(u64.u64_bytes[6] == 0x11);
+	ok1(u64.u64_bytes[5] == 0x22);
+	ok1(u64.u64_bytes[4] == 0x33);
+	ok1(u64.u64_bytes[3] == 0x44);
+	ok1(u64.u64_bytes[2] == 0x55);
+	ok1(u64.u64_bytes[1] == 0x66);
+	ok1(u64.u64_bytes[0] == 0x77);
+
+	u32.u32_bytes[0] = 0x00;
+	u32.u32_bytes[1] = 0x11;
+	u32.u32_bytes[2] = 0x22;
+	u32.u32_bytes[3] = 0x33;
+	u32.u32 = swab_u32(u32.u32);
+	ok1(u32.u32_bytes[3] == 0x00);
+	ok1(u32.u32_bytes[2] == 0x11);
+	ok1(u32.u32_bytes[1] == 0x22);
+	ok1(u32.u32_bytes[0] == 0x33);
+
+	u16.u16_bytes[0] = 0x00;
+	u16.u16_bytes[1] = 0x11;
+	u16.u16 = swab_u16(u16.u16);
+	ok1(u16.u16_bytes[1] == 0x00);
+	ok1(u16.u16_bytes[0] == 0x11);
+
+	/* Endian tests. */
+	u64.u64 = cpu_to_le64(0x0011223344556677ULL);
+	ok1(u64.u64_bytes[0] == 0x77);
+	ok1(u64.u64_bytes[1] == 0x66);
+	ok1(u64.u64_bytes[2] == 0x55);
+	ok1(u64.u64_bytes[3] == 0x44);
+	ok1(u64.u64_bytes[4] == 0x33);
+	ok1(u64.u64_bytes[5] == 0x22);
+	ok1(u64.u64_bytes[6] == 0x11);
+	ok1(u64.u64_bytes[7] == 0x00);
+	ok1(le64_to_cpu(u64.u64) == 0x0011223344556677ULL);
+
+	u64.u64 = cpu_to_be64(0x0011223344556677ULL);
+	ok1(u64.u64_bytes[7] == 0x77);
+	ok1(u64.u64_bytes[6] == 0x66);
+	ok1(u64.u64_bytes[5] == 0x55);
+	ok1(u64.u64_bytes[4] == 0x44);
+	ok1(u64.u64_bytes[3] == 0x33);
+	ok1(u64.u64_bytes[2] == 0x22);
+	ok1(u64.u64_bytes[1] == 0x11);
+	ok1(u64.u64_bytes[0] == 0x00);
+	ok1(be64_to_cpu(u64.u64) == 0x0011223344556677ULL);
+
+	u32.u32 = cpu_to_le32(0x00112233);
+	ok1(u32.u32_bytes[0] == 0x33);
+	ok1(u32.u32_bytes[1] == 0x22);
+	ok1(u32.u32_bytes[2] == 0x11);
+	ok1(u32.u32_bytes[3] == 0x00);
+	ok1(le32_to_cpu(u32.u32) == 0x00112233);
+
+	u32.u32 = cpu_to_be32(0x00112233);
+	ok1(u32.u32_bytes[3] == 0x33);
+	ok1(u32.u32_bytes[2] == 0x22);
+	ok1(u32.u32_bytes[1] == 0x11);
+	ok1(u32.u32_bytes[0] == 0x00);
+	ok1(be32_to_cpu(u32.u32) == 0x00112233);
+
+	u16.u16 = cpu_to_le16(0x0011);
+	ok1(u16.u16_bytes[0] == 0x11);
+	ok1(u16.u16_bytes[1] == 0x00);
+	ok1(le16_to_cpu(u16.u16) == 0x0011);
+
+	u16.u16 = cpu_to_be16(0x0011);
+	ok1(u16.u16_bytes[1] == 0x11);
+	ok1(u16.u16_bytes[0] == 0x00);
+	ok1(be16_to_cpu(u16.u16) == 0x0011);
+
+	exit(exit_status());
+}

config.h

@@ -6,3 +6,5 @@
 #define HAVE_ATTRIBUTE_PRINTF 1
 #define HAVE_BUILTIN_TYPES_COMPATIBLE_P 1
 #define HAVE_BUILTIN_CHOOSE_EXPR 1
+#define HAVE_LITTLE_ENDIAN 1
+#define HAVE_BIG_ENDIAN 0