/*
- * Copyright (c) 2008, 2009, 2010 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#include <config.h>
#include "util.h"
#include <errno.h>
+#include <limits.h>
+#include <pthread.h>
#include <stdarg.h>
+#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
+#include <sys/stat.h>
#include <unistd.h>
+#include "byte-order.h"
#include "coverage.h"
+#include "ovs-thread.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(util);
+COVERAGE_DEFINE(util_xalloc);
+
+/* argv[0] without directory names. */
const char *program_name;
+/* Name for the currently running thread or process, for log messages, process
+ * listings, and debuggers. */
+DEFINE_PER_THREAD_MALLOCED_DATA(char *, subprogram_name);
+
+/* --version option output. */
+static char *program_version;
+
+/* Buffer used by ovs_strerror(). */
+DEFINE_PER_THREAD_DATA(struct { char s[128]; }, strerror_buffer, { "" });
+
+void
+ovs_assert_failure(const char *where, const char *function,
+ const char *condition)
+{
+ /* Prevent an infinite loop (or stack overflow) in case VLOG_ABORT happens
+ * to trigger an assertion failure of its own. */
+ static int reentry = 0;
+
+ switch (reentry++) {
+ case 0:
+ VLOG_ABORT("%s: assertion %s failed in %s()",
+ where, condition, function);
+ NOT_REACHED();
+
+ case 1:
+ fprintf(stderr, "%s: assertion %s failed in %s()",
+ where, condition, function);
+ abort();
+
+ default:
+ abort();
+ }
+}
+
void
out_of_memory(void)
{
- ovs_fatal(0, "virtual memory exhausted");
+ ovs_abort(0, "virtual memory exhausted");
}
void *
return s;
}
+/* Similar to strlcpy() from OpenBSD, but it never reads more than 'size - 1'
+ * bytes from 'src' and doesn't return anything. */
void
ovs_strlcpy(char *dst, const char *src, size_t size)
{
if (size > 0) {
- size_t n = strlen(src);
- size_t n_copy = MIN(n, size - 1);
- memcpy(dst, src, n_copy);
- dst[n_copy] = '\0';
+ size_t len = strnlen(src, size - 1);
+ memcpy(dst, src, len);
+ dst[len] = '\0';
+ }
+}
+
+/* Copies 'src' to 'dst'. Reads no more than 'size - 1' bytes from 'src'.
+ * Always null-terminates 'dst' (if 'size' is nonzero), and writes a zero byte
+ * to every otherwise unused byte in 'dst'.
+ *
+ * Except for performance, the following call:
+ * ovs_strzcpy(dst, src, size);
+ * is equivalent to these two calls:
+ * memset(dst, '\0', size);
+ * ovs_strlcpy(dst, src, size);
+ *
+ * (Thus, ovs_strzcpy() is similar to strncpy() without some of the pitfalls.)
+ */
+void
+ovs_strzcpy(char *dst, const char *src, size_t size)
+{
+ if (size > 0) {
+ size_t len = strnlen(src, size - 1);
+ memcpy(dst, src, len);
+ memset(dst + len, '\0', size - len);
}
}
+/* Prints 'format' on stderr, formatting it like printf() does. If 'err_no' is
+ * nonzero, then it is formatted with ovs_retval_to_string() and appended to
+ * the message inside parentheses. Then, terminates with abort().
+ *
+ * This function is preferred to ovs_fatal() in a situation where it would make
+ * sense for a monitoring process to restart the daemon.
+ *
+ * 'format' should not end with a new-line, because this function will add one
+ * itself. */
+void
+ovs_abort(int err_no, const char *format, ...)
+{
+ va_list args;
+
+ va_start(args, format);
+ ovs_abort_valist(err_no, format, args);
+}
+
+/* Same as ovs_abort() except that the arguments are supplied as a va_list. */
+void
+ovs_abort_valist(int err_no, const char *format, va_list args)
+{
+ ovs_error_valist(err_no, format, args);
+ abort();
+}
+
+/* Prints 'format' on stderr, formatting it like printf() does. If 'err_no' is
+ * nonzero, then it is formatted with ovs_retval_to_string() and appended to
+ * the message inside parentheses. Then, terminates with EXIT_FAILURE.
+ *
+ * 'format' should not end with a new-line, because this function will add one
+ * itself. */
void
ovs_fatal(int err_no, const char *format, ...)
{
va_list args;
- fprintf(stderr, "%s: ", program_name);
va_start(args, format);
- vfprintf(stderr, format, args);
- va_end(args);
- if (err_no != 0)
- fprintf(stderr, " (%s)",
- err_no == EOF ? "end of file" : strerror(err_no));
- putc('\n', stderr);
+ ovs_fatal_valist(err_no, format, args);
+}
+/* Same as ovs_fatal() except that the arguments are supplied as a va_list. */
+void
+ovs_fatal_valist(int err_no, const char *format, va_list args)
+{
+ ovs_error_valist(err_no, format, args);
exit(EXIT_FAILURE);
}
+/* Prints 'format' on stderr, formatting it like printf() does. If 'err_no' is
+ * nonzero, then it is formatted with ovs_retval_to_string() and appended to
+ * the message inside parentheses.
+ *
+ * 'format' should not end with a new-line, because this function will add one
+ * itself. */
void
ovs_error(int err_no, const char *format, ...)
{
- int save_errno = errno;
va_list args;
- fprintf(stderr, "%s: ", program_name);
va_start(args, format);
- vfprintf(stderr, format, args);
+ ovs_error_valist(err_no, format, args);
va_end(args);
+}
+
+/* Same as ovs_error() except that the arguments are supplied as a va_list. */
+void
+ovs_error_valist(int err_no, const char *format, va_list args)
+{
+ const char *subprogram_name = get_subprogram_name();
+ int save_errno = errno;
+
+ if (subprogram_name[0]) {
+ fprintf(stderr, "%s(%s): ", program_name, subprogram_name);
+ } else {
+ fprintf(stderr, "%s: ", program_name);
+ }
+
+ vfprintf(stderr, format, args);
if (err_no != 0) {
- fprintf(stderr, " (%s)",
- err_no == EOF ? "end of file" : strerror(err_no));
+ fprintf(stderr, " (%s)", ovs_retval_to_string(err_no));
}
putc('\n', stderr);
errno = save_errno;
}
-/* Sets program_name based on 'argv0'. Should be called at the beginning of
- * main(), as "set_program_name(argv[0]);". */
-void set_program_name(const char *argv0)
+/* Many OVS functions return an int which is one of:
+ * - 0: no error yet
+ * - >0: errno value
+ * - EOF: end of file (not necessarily an error; depends on the function called)
+ *
+ * Returns the appropriate human-readable string. The caller must copy the
+ * string if it wants to hold onto it, as the storage may be overwritten on
+ * subsequent function calls.
+ */
+const char *
+ovs_retval_to_string(int retval)
+{
+ return (!retval ? ""
+ : retval == EOF ? "End of file"
+ : ovs_strerror(retval));
+}
+
+const char *
+ovs_strerror(int error)
+{
+ enum { BUFSIZE = sizeof strerror_buffer_get()->s };
+ int save_errno;
+ char *buffer;
+ char *s;
+
+ save_errno = errno;
+ buffer = strerror_buffer_get()->s;
+
+#if STRERROR_R_CHAR_P
+ /* GNU style strerror_r() might return an immutable static string, or it
+ * might write and return 'buffer', but in either case we can pass the
+ * returned string directly to the caller. */
+ s = strerror_r(error, buffer, BUFSIZE);
+#else /* strerror_r() returns an int. */
+ s = buffer;
+ if (strerror_r(error, buffer, BUFSIZE)) {
+ /* strerror_r() is only allowed to fail on ERANGE (because the buffer
+ * is too short). We don't check the actual failure reason because
+ * POSIX requires strerror_r() to return the error but old glibc
+ * (before 2.13) returns -1 and sets errno. */
+ snprintf(buffer, BUFSIZE, "Unknown error %d", error);
+ }
+#endif
+
+ errno = save_errno;
+
+ return s;
+}
+
+/* Sets global "program_name" and "program_version" variables. Should
+ * be called at the beginning of main() with "argv[0]" as the argument
+ * to 'argv0'.
+ *
+ * 'version' should contain the version of the caller's program. If 'version'
+ * is the same as the VERSION #define, the caller is assumed to be part of Open
+ * vSwitch. Otherwise, it is assumed to be an external program linking against
+ * the Open vSwitch libraries.
+ *
+ * The 'date' and 'time' arguments should likely be called with
+ * "__DATE__" and "__TIME__" to use the time the binary was built.
+ * Alternatively, the "set_program_name" macro may be called to do this
+ * automatically.
+ */
+void
+set_program_name__(const char *argv0, const char *version, const char *date,
+ const char *time)
{
const char *slash = strrchr(argv0, '/');
+
+ assert_single_threaded();
+
program_name = slash ? slash + 1 : argv0;
+
+ free(program_version);
+
+ if (!strcmp(version, VERSION)) {
+ program_version = xasprintf("%s (Open vSwitch) "VERSION"\n"
+ "Compiled %s %s\n",
+ program_name, date, time);
+ } else {
+ program_version = xasprintf("%s %s\n"
+ "Open vSwitch Library "VERSION"\n"
+ "Compiled %s %s\n",
+ program_name, version, date, time);
+ }
+}
+
+/* Returns the name of the currently running thread or process. */
+const char *
+get_subprogram_name(void)
+{
+ const char *name = subprogram_name_get();
+ return name ? name : "";
+}
+
+/* Sets 'name' as the name of the currently running thread or process. (This
+ * appears in log messages.) */
+void
+set_subprogram_name(const char *name)
+{
+ free(subprogram_name_set(xstrdup(name)));
+}
+
+/* Returns a pointer to a string describing the program version. The
+ * caller must not modify or free the returned string.
+ */
+const char *
+get_program_version(void)
+{
+ return program_version;
}
/* Print the version information for the program. */
void
-ovs_print_version(char *date, char *time,
- uint8_t min_ofp, uint8_t max_ofp)
+ovs_print_version(uint8_t min_ofp, uint8_t max_ofp)
{
- printf("%s (Open vSwitch) "VERSION BUILDNR"\n", program_name);
- printf("Compiled %s %s\n", date, time);
+ printf("%s", program_version);
if (min_ofp || max_ofp) {
printf("OpenFlow versions %#x:%#x\n", min_ofp, max_ofp);
}
case 'f': case 'F':
return 0xf;
+
+ default:
+ return -1;
}
+}
+
+/* Returns the integer value of the 'n' hexadecimal digits starting at 's', or
+ * UINT_MAX if one of those "digits" is not really a hex digit. If 'ok' is
+ * nonnull, '*ok' is set to true if the conversion succeeds or to false if a
+ * non-hex digit is detected. */
+unsigned int
+hexits_value(const char *s, size_t n, bool *ok)
+{
+ unsigned int value;
+ size_t i;
- NOT_REACHED();
+ value = 0;
+ for (i = 0; i < n; i++) {
+ int hexit = hexit_value(s[i]);
+ if (hexit < 0) {
+ if (ok) {
+ *ok = false;
+ }
+ return UINT_MAX;
+ }
+ value = (value << 4) + hexit;
+ }
+ if (ok) {
+ *ok = true;
+ }
+ return value;
}
/* Returns the current working directory as a malloc()'d string, or a null
int error = errno;
free(buf);
if (error != ERANGE) {
- VLOG_WARN("getcwd failed (%s)", strerror(error));
+ VLOG_WARN("getcwd failed (%s)", ovs_strerror(error));
return NULL;
}
size *= 2;
}
}
+static char *
+all_slashes_name(const char *s)
+{
+ return xstrdup(s[0] == '/' && s[1] == '/' && s[2] != '/' ? "//"
+ : s[0] == '/' ? "/"
+ : ".");
+}
+
/* Returns the directory name portion of 'file_name' as a malloc()'d string,
* similar to the POSIX dirname() function but thread-safe. */
char *
while (len > 0 && file_name[len - 1] == '/') {
len--;
}
- if (!len) {
- return xstrdup((file_name[0] == '/'
- && file_name[1] == '/'
- && file_name[2] != '/') ? "//"
- : file_name[0] == '/' ? "/"
- : ".");
- } else {
- return xmemdup0(file_name, len);
+ return len ? xmemdup0(file_name, len) : all_slashes_name(file_name);
+}
+
+/* Returns the file name portion of 'file_name' as a malloc()'d string,
+ * similar to the POSIX basename() function but thread-safe. */
+char *
+base_name(const char *file_name)
+{
+ size_t end, start;
+
+ end = strlen(file_name);
+ while (end > 0 && file_name[end - 1] == '/') {
+ end--;
}
+
+ if (!end) {
+ return all_slashes_name(file_name);
+ }
+
+ start = end;
+ while (start > 0 && file_name[start - 1] != '/') {
+ start--;
+ }
+
+ return xmemdup0(file_name + start, end - start);
}
/* If 'file_name' starts with '/', returns a copy of 'file_name'. Otherwise,
}
}
+/* Like readlink(), but returns the link name as a null-terminated string in
+ * allocated memory that the caller must eventually free (with free()).
+ * Returns NULL on error, in which case errno is set appropriately. */
+char *
+xreadlink(const char *filename)
+{
+ size_t size;
+
+ for (size = 64; ; size *= 2) {
+ char *buf = xmalloc(size);
+ ssize_t retval = readlink(filename, buf, size);
+ int error = errno;
+
+ if (retval >= 0 && retval < size) {
+ buf[retval] = '\0';
+ return buf;
+ }
+
+ free(buf);
+ if (retval < 0) {
+ errno = error;
+ return NULL;
+ }
+ }
+}
+
+/* Returns a version of 'filename' with symlinks in the final component
+ * dereferenced. This differs from realpath() in that:
+ *
+ * - 'filename' need not exist.
+ *
+ * - If 'filename' does exist as a symlink, its referent need not exist.
+ *
+ * - Only symlinks in the final component of 'filename' are dereferenced.
+ *
+ * The caller must eventually free the returned string (with free()). */
+char *
+follow_symlinks(const char *filename)
+{
+ struct stat s;
+ char *fn;
+ int i;
+
+ fn = xstrdup(filename);
+ for (i = 0; i < 10; i++) {
+ char *linkname;
+ char *next_fn;
+
+ if (lstat(fn, &s) != 0 || !S_ISLNK(s.st_mode)) {
+ return fn;
+ }
+
+ linkname = xreadlink(fn);
+ if (!linkname) {
+ VLOG_WARN("%s: readlink failed (%s)",
+ filename, ovs_strerror(errno));
+ return fn;
+ }
+
+ if (linkname[0] == '/') {
+ /* Target of symlink is absolute so use it raw. */
+ next_fn = linkname;
+ } else {
+ /* Target of symlink is relative so add to 'fn''s directory. */
+ char *dir = dir_name(fn);
+
+ if (!strcmp(dir, ".")) {
+ next_fn = linkname;
+ } else {
+ char *separator = dir[strlen(dir) - 1] == '/' ? "" : "/";
+ next_fn = xasprintf("%s%s%s", dir, separator, linkname);
+ free(linkname);
+ }
+
+ free(dir);
+ }
+
+ free(fn);
+ fn = next_fn;
+ }
+
+ VLOG_WARN("%s: too many levels of symlinks", filename);
+ free(fn);
+ return xstrdup(filename);
+}
/* Pass a value to this function if it is marked with
* __attribute__((warn_unused_result)) and you genuinely want to ignore
* its return value. (Note that every scalar type can be implicitly
* converted to bool.) */
void ignore(bool x OVS_UNUSED) { }
+
+/* Returns an appropriate delimiter for inserting just before the 0-based item
+ * 'index' in a list that has 'total' items in it. */
+const char *
+english_list_delimiter(size_t index, size_t total)
+{
+ return (index == 0 ? ""
+ : index < total - 1 ? ", "
+ : total > 2 ? ", and "
+ : " and ");
+}
+
+/* Given a 32 bit word 'n', calculates floor(log_2('n')). This is equivalent
+ * to finding the bit position of the most significant one bit in 'n'. It is
+ * an error to call this function with 'n' == 0. */
+int
+log_2_floor(uint32_t n)
+{
+ ovs_assert(n);
+
+#if !defined(UINT_MAX) || !defined(UINT32_MAX)
+#error "Someone screwed up the #includes."
+#elif __GNUC__ >= 4 && UINT_MAX == UINT32_MAX
+ return 31 - __builtin_clz(n);
+#else
+ {
+ int log = 0;
+
+#define BIN_SEARCH_STEP(BITS) \
+ if (n >= (1 << BITS)) { \
+ log += BITS; \
+ n >>= BITS; \
+ }
+ BIN_SEARCH_STEP(16);
+ BIN_SEARCH_STEP(8);
+ BIN_SEARCH_STEP(4);
+ BIN_SEARCH_STEP(2);
+ BIN_SEARCH_STEP(1);
+#undef BIN_SEARCH_STEP
+ return log;
+ }
+#endif
+}
+
+/* Given a 32 bit word 'n', calculates ceil(log_2('n')). It is an error to
+ * call this function with 'n' == 0. */
+int
+log_2_ceil(uint32_t n)
+{
+ return log_2_floor(n) + !is_pow2(n);
+}
+
+/* Returns the number of trailing 0-bits in 'n'. Undefined if 'n' == 0. */
+#if !defined(UINT_MAX) || !defined(UINT32_MAX)
+#error "Someone screwed up the #includes."
+#elif __GNUC__ >= 4 && UINT_MAX == UINT32_MAX
+/* Defined inline in util.h. */
+#else
+static int
+raw_ctz(uint32_t n)
+{
+ unsigned int k;
+ int count = 31;
+
+#define CTZ_STEP(X) \
+ k = n << (X); \
+ if (k) { \
+ count -= X; \
+ n = k; \
+ }
+ CTZ_STEP(16);
+ CTZ_STEP(8);
+ CTZ_STEP(4);
+ CTZ_STEP(2);
+ CTZ_STEP(1);
+#undef CTZ_STEP
+
+ return count;
+}
+#endif
+
+/* Returns the number of 1-bits in 'x', between 0 and 32 inclusive. */
+unsigned int
+popcount(uint32_t x)
+{
+ /* In my testing, this implementation is over twice as fast as any other
+ * portable implementation that I tried, including GCC 4.4
+ * __builtin_popcount(), although nonportable asm("popcnt") was over 50%
+ * faster. */
+#define INIT1(X) \
+ ((((X) & (1 << 0)) != 0) + \
+ (((X) & (1 << 1)) != 0) + \
+ (((X) & (1 << 2)) != 0) + \
+ (((X) & (1 << 3)) != 0) + \
+ (((X) & (1 << 4)) != 0) + \
+ (((X) & (1 << 5)) != 0) + \
+ (((X) & (1 << 6)) != 0) + \
+ (((X) & (1 << 7)) != 0))
+#define INIT2(X) INIT1(X), INIT1((X) + 1)
+#define INIT4(X) INIT2(X), INIT2((X) + 2)
+#define INIT8(X) INIT4(X), INIT4((X) + 4)
+#define INIT16(X) INIT8(X), INIT8((X) + 8)
+#define INIT32(X) INIT16(X), INIT16((X) + 16)
+#define INIT64(X) INIT32(X), INIT32((X) + 32)
+
+ static const uint8_t popcount8[256] = {
+ INIT64(0), INIT64(64), INIT64(128), INIT64(192)
+ };
+
+ return (popcount8[x & 0xff] +
+ popcount8[(x >> 8) & 0xff] +
+ popcount8[(x >> 16) & 0xff] +
+ popcount8[x >> 24]);
+}
+
+/* Returns true if the 'n' bytes starting at 'p' are zeros. */
+bool
+is_all_zeros(const uint8_t *p, size_t n)
+{
+ size_t i;
+
+ for (i = 0; i < n; i++) {
+ if (p[i] != 0x00) {
+ return false;
+ }
+ }
+ return true;
+}
+
+/* Returns true if the 'n' bytes starting at 'p' are 0xff. */
+bool
+is_all_ones(const uint8_t *p, size_t n)
+{
+ size_t i;
+
+ for (i = 0; i < n; i++) {
+ if (p[i] != 0xff) {
+ return false;
+ }
+ }
+ return true;
+}
+
+/* Copies 'n_bits' bits starting from bit 'src_ofs' in 'src' to the 'n_bits'
+ * starting from bit 'dst_ofs' in 'dst'. 'src' is 'src_len' bytes long and
+ * 'dst' is 'dst_len' bytes long.
+ *
+ * If you consider all of 'src' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in src[src_len - 1], bit 1 is the bit with value 2, bit 2 is
+ * the bit with value 4, ..., bit 8 is the bit with value 1 in src[src_len -
+ * 2], and so on. Similarly for 'dst'.
+ *
+ * Required invariants:
+ * src_ofs + n_bits <= src_len * 8
+ * dst_ofs + n_bits <= dst_len * 8
+ * 'src' and 'dst' must not overlap.
+ */
+void
+bitwise_copy(const void *src_, unsigned int src_len, unsigned int src_ofs,
+ void *dst_, unsigned int dst_len, unsigned int dst_ofs,
+ unsigned int n_bits)
+{
+ const uint8_t *src = src_;
+ uint8_t *dst = dst_;
+
+ src += src_len - (src_ofs / 8 + 1);
+ src_ofs %= 8;
+
+ dst += dst_len - (dst_ofs / 8 + 1);
+ dst_ofs %= 8;
+
+ if (src_ofs == 0 && dst_ofs == 0) {
+ unsigned int n_bytes = n_bits / 8;
+ if (n_bytes) {
+ dst -= n_bytes - 1;
+ src -= n_bytes - 1;
+ memcpy(dst, src, n_bytes);
+
+ n_bits %= 8;
+ src--;
+ dst--;
+ }
+ if (n_bits) {
+ uint8_t mask = (1 << n_bits) - 1;
+ *dst = (*dst & ~mask) | (*src & mask);
+ }
+ } else {
+ while (n_bits > 0) {
+ unsigned int max_copy = 8 - MAX(src_ofs, dst_ofs);
+ unsigned int chunk = MIN(n_bits, max_copy);
+ uint8_t mask = ((1 << chunk) - 1) << dst_ofs;
+
+ *dst &= ~mask;
+ *dst |= ((*src >> src_ofs) << dst_ofs) & mask;
+
+ src_ofs += chunk;
+ if (src_ofs == 8) {
+ src--;
+ src_ofs = 0;
+ }
+ dst_ofs += chunk;
+ if (dst_ofs == 8) {
+ dst--;
+ dst_ofs = 0;
+ }
+ n_bits -= chunk;
+ }
+ }
+}
+
+/* Zeros the 'n_bits' bits starting from bit 'dst_ofs' in 'dst'. 'dst' is
+ * 'dst_len' bytes long.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
+ * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
+ * 2], and so on.
+ *
+ * Required invariant:
+ * dst_ofs + n_bits <= dst_len * 8
+ */
+void
+bitwise_zero(void *dst_, unsigned int dst_len, unsigned dst_ofs,
+ unsigned int n_bits)
+{
+ uint8_t *dst = dst_;
+
+ if (!n_bits) {
+ return;
+ }
+
+ dst += dst_len - (dst_ofs / 8 + 1);
+ dst_ofs %= 8;
+
+ if (dst_ofs) {
+ unsigned int chunk = MIN(n_bits, 8 - dst_ofs);
+
+ *dst &= ~(((1 << chunk) - 1) << dst_ofs);
+
+ n_bits -= chunk;
+ if (!n_bits) {
+ return;
+ }
+
+ dst--;
+ }
+
+ while (n_bits >= 8) {
+ *dst-- = 0;
+ n_bits -= 8;
+ }
+
+ if (n_bits) {
+ *dst &= ~((1 << n_bits) - 1);
+ }
+}
+
+/* Sets to 1 all of the 'n_bits' bits starting from bit 'dst_ofs' in 'dst'.
+ * 'dst' is 'dst_len' bytes long.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
+ * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
+ * 2], and so on.
+ *
+ * Required invariant:
+ * dst_ofs + n_bits <= dst_len * 8
+ */
+void
+bitwise_one(void *dst_, unsigned int dst_len, unsigned dst_ofs,
+ unsigned int n_bits)
+{
+ uint8_t *dst = dst_;
+
+ if (!n_bits) {
+ return;
+ }
+
+ dst += dst_len - (dst_ofs / 8 + 1);
+ dst_ofs %= 8;
+
+ if (dst_ofs) {
+ unsigned int chunk = MIN(n_bits, 8 - dst_ofs);
+
+ *dst |= ((1 << chunk) - 1) << dst_ofs;
+
+ n_bits -= chunk;
+ if (!n_bits) {
+ return;
+ }
+
+ dst--;
+ }
+
+ while (n_bits >= 8) {
+ *dst-- = 0xff;
+ n_bits -= 8;
+ }
+
+ if (n_bits) {
+ *dst |= (1 << n_bits) - 1;
+ }
+}
+
+/* Scans the 'n_bits' bits starting from bit 'dst_ofs' in 'dst' for 1-bits.
+ * Returns false if any 1-bits are found, otherwise true. 'dst' is 'dst_len'
+ * bytes long.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
+ * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
+ * 2], and so on.
+ *
+ * Required invariant:
+ * dst_ofs + n_bits <= dst_len * 8
+ */
+bool
+bitwise_is_all_zeros(const void *p_, unsigned int len, unsigned int ofs,
+ unsigned int n_bits)
+{
+ const uint8_t *p = p_;
+
+ if (!n_bits) {
+ return true;
+ }
+
+ p += len - (ofs / 8 + 1);
+ ofs %= 8;
+
+ if (ofs) {
+ unsigned int chunk = MIN(n_bits, 8 - ofs);
+
+ if (*p & (((1 << chunk) - 1) << ofs)) {
+ return false;
+ }
+
+ n_bits -= chunk;
+ if (!n_bits) {
+ return true;
+ }
+
+ p--;
+ }
+
+ while (n_bits >= 8) {
+ if (*p) {
+ return false;
+ }
+ n_bits -= 8;
+ p--;
+ }
+
+ if (n_bits && *p & ((1 << n_bits) - 1)) {
+ return false;
+ }
+
+ return true;
+}
+
+/* Copies the 'n_bits' low-order bits of 'value' into the 'n_bits' bits
+ * starting at bit 'dst_ofs' in 'dst', which is 'dst_len' bytes long.
+ *
+ * If you consider all of 'dst' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in dst[dst_len - 1], bit 1 is the bit with value 2, bit 2 is
+ * the bit with value 4, ..., bit 8 is the bit with value 1 in dst[dst_len -
+ * 2], and so on.
+ *
+ * Required invariants:
+ * dst_ofs + n_bits <= dst_len * 8
+ * n_bits <= 64
+ */
+void
+bitwise_put(uint64_t value,
+ void *dst, unsigned int dst_len, unsigned int dst_ofs,
+ unsigned int n_bits)
+{
+ ovs_be64 n_value = htonll(value);
+ bitwise_copy(&n_value, sizeof n_value, 0,
+ dst, dst_len, dst_ofs,
+ n_bits);
+}
+
+/* Returns the value of the 'n_bits' bits starting at bit 'src_ofs' in 'src',
+ * which is 'src_len' bytes long.
+ *
+ * If you consider all of 'src' to be a single unsigned integer in network byte
+ * order, then bit N is the bit with value 2**N. That is, bit 0 is the bit
+ * with value 1 in src[src_len - 1], bit 1 is the bit with value 2, bit 2 is
+ * the bit with value 4, ..., bit 8 is the bit with value 1 in src[src_len -
+ * 2], and so on.
+ *
+ * Required invariants:
+ * src_ofs + n_bits <= src_len * 8
+ * n_bits <= 64
+ */
+uint64_t
+bitwise_get(const void *src, unsigned int src_len,
+ unsigned int src_ofs, unsigned int n_bits)
+{
+ ovs_be64 value = htonll(0);
+
+ bitwise_copy(src, src_len, src_ofs,
+ &value, sizeof value, 0,
+ n_bits);
+ return ntohll(value);
+}