/*
* Copyright © 2009,2010 Red Hat, Inc.
* Copyright © 2011,2012 Google, Inc.
*
* This is part of HarfBuzz, a text shaping library.
*
* Permission is hereby granted, without written agreement and without
* license or royalty fees, to use, copy, modify, and distribute this
* software and its documentation for any purpose, provided that the
* above copyright notice and the following two paragraphs appear in
* all copies of this software.
*
* IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
* DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
* ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
* IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE.
*
* THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
* BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE PROVIDED HEREUNDER IS
* ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
* PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
*
* Red Hat Author(s): Behdad Esfahbod
* Google Author(s): Behdad Esfahbod
*/
#include "hb-private.hh"
#include "hb-mutex-private.hh"
#include "hb-object-private.hh"
#include <locale.h>
/* hb_options_t */
hb_options_union_t _hb_options;
void
_hb_options_init (void)
{
hb_options_union_t u;
u.i = 0;
u.opts.initialized = 1;
char *c = getenv ("HB_OPTIONS");
u.opts.uniscribe_bug_compatible = c && strstr (c, "uniscribe-bug-compatible");
/* This is idempotent and threadsafe. */
_hb_options = u;
}
/* hb_tag_t */
/**
* hb_tag_from_string:
* @str: (array length=len) (element-type uint8_t):
* @len:
*
*
*
* Return value:
*
* Since: 0.9.2
**/
hb_tag_t
hb_tag_from_string (const char *str, int len)
{
char tag[4];
unsigned int i;
if (!str || !len || !*str)
return HB_TAG_NONE;
if (len < 0 || len > 4)
len = 4;
for (i = 0; i < (unsigned) len && str[i]; i++)
tag[i] = str[i];
for (; i < 4; i++)
tag[i] = ' ';
return HB_TAG_CHAR4 (tag);
}
/**
* hb_tag_to_string:
* @tag:
* @buf: (out caller-allocates) (array fixed-size=4) (element-type uint8_t):
*
*
*
* Since: 0.9.5
**/
void
hb_tag_to_string (hb_tag_t tag, char *buf)
{
buf[0] = (char) (uint8_t) (tag >> 24);
buf[1] = (char) (uint8_t) (tag >> 16);
buf[2] = (char) (uint8_t) (tag >> 8);
buf[3] = (char) (uint8_t) (tag >> 0);
}
/* hb_direction_t */
const char direction_strings[][4] = {
"ltr",
"rtl",
"ttb",
"btt"
};
/**
* hb_direction_from_string:
* @str: (array length=len) (element-type uint8_t):
* @len:
*
*
*
* Return value:
*
* Since: 0.9.2
**/
hb_direction_t
hb_direction_from_string (const char *str, int len)
{
if (unlikely (!str || !len || !*str))
return HB_DIRECTION_INVALID;
/* Lets match loosely: just match the first letter, such that
* all of "ltr", "left-to-right", etc work!
*/
char c = TOLOWER (str[0]);
for (unsigned int i = 0; i < ARRAY_LENGTH (direction_strings); i++)
if (c == direction_strings[i][0])
return (hb_direction_t) (HB_DIRECTION_LTR + i);
return HB_DIRECTION_INVALID;
}
/**
* hb_direction_to_string:
* @direction:
*
*
*
* Return value: (transfer none):
*
* Since: 0.9.2
**/
const char *
hb_direction_to_string (hb_direction_t direction)
{
if (likely ((unsigned int) (direction - HB_DIRECTION_LTR)
< ARRAY_LENGTH (direction_strings)))
return direction_strings[direction - HB_DIRECTION_LTR];
return "invalid";
}
/* hb_language_t */
struct hb_language_impl_t {
const char s[1];
};
static const char canon_map[256] = {
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, '-', 0, 0,
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 0, 0, 0, 0, 0, 0,
'-', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 0, 0, 0, 0, '-',
0, 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', 0, 0, 0, 0, 0
};
static bool
lang_equal (hb_language_t v1,
const void *v2)
{
const unsigned char *p1 = (const unsigned char *) v1;
const unsigned char *p2 = (const unsigned char *) v2;
while (*p1 && *p1 == canon_map[*p2]) {
p1++;
p2++;
}
return *p1 == canon_map[*p2];
}
#if 0
static unsigned int
lang_hash (const void *key)
{
const unsigned char *p = key;
unsigned int h = 0;
while (canon_map[*p])
{
h = (h << 5) - h + canon_map[*p];
p++;
}
return h;
}
#endif
struct hb_language_item_t {
struct hb_language_item_t *next;
hb_language_t lang;
inline bool operator == (const char *s) const {
return lang_equal (lang, s);
}
inline hb_language_item_t & operator = (const char *s) {
/* If a custom allocated is used calling strdup() pairs
badly with a call to the custom free() in finish() below.
Therefore don't call strdup(), implement its behavior.
*/
size_t len = strlen(s) + 1;
lang = (hb_language_t) malloc(len);
if (likely (lang))
{
memcpy((unsigned char *) lang, s, len);
for (unsigned char *p = (unsigned char *) lang; *p; p++)
*p = canon_map[*p];
}
return *this;
}
void finish (void) { free ((void *) lang); }
};
/* Thread-safe lock-free language list */
static hb_language_item_t *langs;
#ifdef HB_USE_ATEXIT
static
void free_langs (void)
{
while (langs) {
hb_language_item_t *next = langs->next;
langs->finish ();
free (langs);
langs = next;
}
}
#endif
static hb_language_item_t *
lang_find_or_insert (const char *key)
{
retry:
hb_language_item_t *first_lang = (hb_language_item_t *) hb_atomic_ptr_get (&langs);
for (hb_language_item_t *lang = first_lang; lang; lang = lang->next)
if (*lang == key)
return lang;
/* Not found; allocate one. */
hb_language_item_t *lang = (hb_language_item_t *) calloc (1, sizeof (hb_language_item_t));
if (unlikely (!lang))
return NULL;
lang->next = first_lang;
*lang = key;
if (unlikely (!lang->lang))
{
free (lang);
return NULL;
}
if (!hb_atomic_ptr_cmpexch (&langs, first_lang, lang)) {
lang->finish ();
free (lang);
goto retry;
}
#ifdef HB_USE_ATEXIT
if (!first_lang)
atexit (free_langs); /* First person registers atexit() callback. */
#endif
return lang;
}
/**
* hb_language_from_string:
* @str: (array length=len) (element-type uint8_t): a string representing
* ISO 639 language code
* @len: length of the @str, or -1 if it is %NULL-terminated.
*
* Converts @str representing an ISO 639 language code to the corresponding
* #hb_language_t.
*
* Return value: (transfer none):
* The #hb_language_t corresponding to the ISO 639 language code.
*
* Since: 0.9.2
**/
hb_language_t
hb_language_from_string (const char *str, int len)
{
if (!str || !len || !*str)
return HB_LANGUAGE_INVALID;
hb_language_item_t *item = NULL;
if (len >= 0)
{
/* NUL-terminate it. */
char strbuf[64];
len = MIN (len, (int) sizeof (strbuf) - 1);
memcpy (strbuf, str, len);
strbuf[len] = '\0';
item = lang_find_or_insert (strbuf);
}
else
item = lang_find_or_insert (str);
return likely (item) ? item->lang : HB_LANGUAGE_INVALID;
}
/**
* hb_language_to_string:
* @language: an #hb_language_t to convert.
*
* See hb_language_from_string().
*
* Return value: (transfer none):
* A %NULL-terminated string representing the @language. Must not be freed by
* the caller.
*
* Since: 0.9.2
**/
const char *
hb_language_to_string (hb_language_t language)
{
/* This is actually NULL-safe! */
return language->s;
}
/**
* hb_language_get_default:
*
*
*
* Return value: (transfer none):
*
* Since: 0.9.2
**/
hb_language_t
hb_language_get_default (void)
{
static hb_language_t default_language = HB_LANGUAGE_INVALID;
hb_language_t language = (hb_language_t) hb_atomic_ptr_get (&default_language);
if (unlikely (language == HB_LANGUAGE_INVALID)) {
language = hb_language_from_string (setlocale (LC_CTYPE, NULL), -1);
(void) hb_atomic_ptr_cmpexch (&default_language, HB_LANGUAGE_INVALID, language);
}
return default_language;
}
/* hb_script_t */
/**
* hb_script_from_iso15924_tag:
* @tag: an #hb_tag_t representing an ISO 15924 tag.
*
* Converts an ISO 15924 script tag to a corresponding #hb_script_t.
*
* Return value:
* An #hb_script_t corresponding to the ISO 15924 tag.
*
* Since: 0.9.2
**/
hb_script_t
hb_script_from_iso15924_tag (hb_tag_t tag)
{
if (unlikely (tag == HB_TAG_NONE))
return HB_SCRIPT_INVALID;
/* Be lenient, adjust case (one capital letter followed by three small letters) */
tag = (tag & 0xDFDFDFDFu) | 0x00202020u;
switch (tag) {
/* These graduated from the 'Q' private-area codes, but
* the old code is still aliased by Unicode, and the Qaai
* one in use by ICU. */
case HB_TAG('Q','a','a','i'): return HB_SCRIPT_INHERITED;
case HB_TAG('Q','a','a','c'): return HB_SCRIPT_COPTIC;
/* Script variants from http://unicode.org/iso15924/ */
case HB_TAG('C','y','r','s'): return HB_SCRIPT_CYRILLIC;
case HB_TAG('L','a','t','f'): return HB_SCRIPT_LATIN;
case HB_TAG('L','a','t','g'): return HB_SCRIPT_LATIN;
case HB_TAG('S','y','r','e'): return HB_SCRIPT_SYRIAC;
case HB_TAG('S','y','r','j'): return HB_SCRIPT_SYRIAC;
case HB_TAG('S','y','r','n'): return HB_SCRIPT_SYRIAC;
}
/* If it looks right, just use the tag as a script */
if (((uint32_t) tag & 0xE0E0E0E0u) == 0x40606060u)
return (hb_script_t) tag;
/* Otherwise, return unknown */
return HB_SCRIPT_UNKNOWN;
}
/**
* hb_script_from_string:
* @str: (array length=len) (element-type uint8_t): a string representing an
* ISO 15924 tag.
* @len: length of the @str, or -1 if it is %NULL-terminated.
*
* Converts a string @str representing an ISO 15924 script tag to a
* corresponding #hb_script_t. Shorthand for hb_tag_from_string() then
* hb_script_from_iso15924_tag().
*
* Return value:
* An #hb_script_t corresponding to the ISO 15924 tag.
*
* Since: 0.9.2
**/
hb_script_t
hb_script_from_string (const char *str, int len)
{
return hb_script_from_iso15924_tag (hb_tag_from_string (str, len));
}
/**
* hb_script_to_iso15924_tag:
* @script: an #hb_script_ to convert.
*
* See hb_script_from_iso15924_tag().
*
* Return value:
* An #hb_tag_t representing an ISO 15924 script tag.
*
* Since: 0.9.2
**/
hb_tag_t
hb_script_to_iso15924_tag (hb_script_t script)
{
return (hb_tag_t) script;
}
/**
* hb_script_get_horizontal_direction:
* @script:
*
*
*
* Return value:
*
* Since: 0.9.2
**/
hb_direction_t
hb_script_get_horizontal_direction (hb_script_t script)
{
/* http://goo.gl/x9ilM */
switch ((hb_tag_t) script)
{
/* Unicode-1.1 additions */
case HB_SCRIPT_ARABIC:
case HB_SCRIPT_HEBREW:
/* Unicode-3.0 additions */
case HB_SCRIPT_SYRIAC:
case HB_SCRIPT_THAANA:
/* Unicode-4.0 additions */
case HB_SCRIPT_CYPRIOT:
/* Unicode-4.1 additions */
case HB_SCRIPT_KHAROSHTHI:
/* Unicode-5.0 additions */
case HB_SCRIPT_PHOENICIAN:
case HB_SCRIPT_NKO:
/* Unicode-5.1 additions */
case HB_SCRIPT_LYDIAN:
/* Unicode-5.2 additions */
case HB_SCRIPT_AVESTAN:
case HB_SCRIPT_IMPERIAL_ARAMAIC:
case HB_SCRIPT_INSCRIPTIONAL_PAHLAVI:
case HB_SCRIPT_INSCRIPTIONAL_PARTHIAN:
case HB_SCRIPT_OLD_SOUTH_ARABIAN:
case HB_SCRIPT_OLD_TURKIC:
case HB_SCRIPT_SAMARITAN:
/* Unicode-6.0 additions */
case HB_SCRIPT_MANDAIC:
/* Unicode-6.1 additions */
case HB_SCRIPT_MEROITIC_CURSIVE:
case HB_SCRIPT_MEROITIC_HIEROGLYPHS:
/* Unicode-7.0 additions */
case HB_SCRIPT_MANICHAEAN:
case HB_SCRIPT_MENDE_KIKAKUI:
case HB_SCRIPT_NABATAEAN:
case HB_SCRIPT_OLD_NORTH_ARABIAN:
case HB_SCRIPT_PALMYRENE:
case HB_SCRIPT_PSALTER_PAHLAVI:
/* Unicode-8.0 additions */
case HB_SCRIPT_OLD_HUNGARIAN:
/* Unicode-9.0 additions */
case HB_SCRIPT_ADLAM:
return HB_DIRECTION_RTL;
}
return HB_DIRECTION_LTR;
}
/* hb_user_data_array_t */
bool
hb_user_data_array_t::set (hb_user_data_key_t *key,
void * data,
hb_destroy_func_t destroy,
hb_bool_t replace)
{
if (!key)
return false;
if (replace) {
if (!data && !destroy) {
items.remove (key, lock);
return true;
}
}
hb_user_data_item_t item = {key, data, destroy};
bool ret = !!items.replace_or_insert (item, lock, (bool) replace);
return ret;
}
void *
hb_user_data_array_t::get (hb_user_data_key_t *key)
{
hb_user_data_item_t item = {NULL, NULL, NULL};
return items.find (key, &item, lock) ? item.data : NULL;
}
/* hb_version */
/**
* hb_version:
* @major: (out): Library major version component.
* @minor: (out): Library minor version component.
* @micro: (out): Library micro version component.
*
* Returns library version as three integer components.
*
* Since: 0.9.2
**/
void
hb_version (unsigned int *major,
unsigned int *minor,
unsigned int *micro)
{
*major = HB_VERSION_MAJOR;
*minor = HB_VERSION_MINOR;
*micro = HB_VERSION_MICRO;
}
/**
* hb_version_string:
*
* Returns library version as a string with three components.
*
* Return value: library version string.
*
* Since: 0.9.2
**/
const char *
hb_version_string (void)
{
return HB_VERSION_STRING;
}
/**
* hb_version_atleast:
* @major:
* @minor:
* @micro:
*
*
*
* Return value:
*
* Since: 0.9.30
**/
hb_bool_t
hb_version_atleast (unsigned int major,
unsigned int minor,
unsigned int micro)
{
return HB_VERSION_ATLEAST (major, minor, micro);
}
/* hb_feature_t and hb_variation_t */
static bool
parse_space (const char **pp, const char *end)
{
while (*pp < end && ISSPACE (**pp))
(*pp)++;
return true;
}
static bool
parse_char (const char **pp, const char *end, char c)
{
parse_space (pp, end);
if (*pp == end || **pp != c)
return false;
(*pp)++;
return true;
}
static bool
parse_uint (const char **pp, const char *end, unsigned int *pv)
{
char buf[32];
unsigned int len = MIN (ARRAY_LENGTH (buf) - 1, (unsigned int) (end - *pp));
strncpy (buf, *pp, len);
buf[len] = '\0';
char *p = buf;
char *pend = p;
unsigned int v;
/* Intentionally use strtol instead of strtoul, such that
* -1 turns into "big number"... */
errno = 0;
v = strtol (p, &pend, 0);
if (errno || p == pend)
return false;
*pv = v;
*pp += pend - p;
return true;
}
static bool
parse_uint32 (const char **pp, const char *end, uint32_t *pv)
{
char buf[32];
unsigned int len = MIN (ARRAY_LENGTH (buf) - 1, (unsigned int) (end - *pp));
strncpy (buf, *pp, len);
buf[len] = '\0';
char *p = buf;
char *pend = p;
unsigned int v;
/* Intentionally use strtol instead of strtoul, such that
* -1 turns into "big number"... */
errno = 0;
v = strtol (p, &pend, 0);
if (errno || p == pend)
return false;
*pv = v;
*pp += pend - p;
return true;
}
static bool
parse_float (const char **pp, const char *end, float *pv)
{
char buf[32];
unsigned int len = MIN (ARRAY_LENGTH (buf) - 1, (unsigned int) (end - *pp));
strncpy (buf, *pp, len);
buf[len] = '\0';
char *p = buf;
char *pend = p;
float v;
errno = 0;
v = strtod (p, &pend);
if (errno || p == pend)
return false;
*pv = v;
*pp += pend - p;
return true;
}
static bool
parse_bool (const char **pp, const char *end, uint32_t *pv)
{
parse_space (pp, end);
const char *p = *pp;
while (*pp < end && ISALPHA(**pp))
(*pp)++;
/* CSS allows on/off as aliases 1/0. */
if (*pp - p == 2 || 0 == strncmp (p, "on", 2))
*pv = 1;
else if (*pp - p == 3 || 0 == strncmp (p, "off", 2))
*pv = 0;
else
return false;
return true;
}
/* hb_feature_t */
static bool
parse_feature_value_prefix (const char **pp, const char *end, hb_feature_t *feature)
{
if (parse_char (pp, end, '-'))
feature->value = 0;
else {
parse_char (pp, end, '+');
feature->value = 1;
}
return true;
}
static bool
parse_tag (const char **pp, const char *end, hb_tag_t *tag)
{
parse_space (pp, end);
char quote = 0;
if (*pp < end && (**pp == '\'' || **pp == '"'))
{
quote = **pp;
(*pp)++;
}
const char *p = *pp;
while (*pp < end && ISALNUM(**pp))
(*pp)++;
if (p == *pp || *pp - p > 4)
return false;
*tag = hb_tag_from_string (p, *pp - p);
if (quote)
{
/* CSS expects exactly four bytes. And we only allow quotations for
* CSS compatibility. So, enforce the length. */
if (*pp - p != 4)
return false;
if (*pp == end || **pp != quote)
return false;
(*pp)++;
}
return true;
}
static bool
parse_feature_indices (const char **pp, const char *end, hb_feature_t *feature)
{
parse_space (pp, end);
bool has_start;
feature->start = 0;
feature->end = (unsigned int) -1;
if (!parse_char (pp, end, '['))
return true;
has_start = parse_uint (pp, end, &feature->start);
if (parse_char (pp, end, ':')) {
parse_uint (pp, end, &feature->end);
} else {
if (has_start)
feature->end = feature->start + 1;
}
return parse_char (pp, end, ']');
}
static bool
parse_feature_value_postfix (const char **pp, const char *end, hb_feature_t *feature)
{
bool had_equal = parse_char (pp, end, '=');
bool had_value = parse_uint32 (pp, end, &feature->value) ||
parse_bool (pp, end, &feature->value);
/* CSS doesn't use equal-sign between tag and value.
* If there was an equal-sign, then there *must* be a value.
* A value without an eqaul-sign is ok, but not required. */
return !had_equal || had_value;
}
static bool
parse_one_feature (const char **pp, const char *end, hb_feature_t *feature)
{
return parse_feature_value_prefix (pp, end, feature) &&
parse_tag (pp, end, &feature->tag) &&
parse_feature_indices (pp, end, feature) &&
parse_feature_value_postfix (pp, end, feature) &&
parse_space (pp, end) &&
*pp == end;
}
/**
* hb_feature_from_string:
* @str: (array length=len) (element-type uint8_t): a string to parse
* @len: length of @str, or -1 if string is %NULL terminated
* @feature: (out): the #hb_feature_t to initialize with the parsed values
*
* Parses a string into a #hb_feature_t.
*
* TODO: document the syntax here.
*
* Return value:
* %true if @str is successfully parsed, %false otherwise.
*
* Since: 0.9.5
**/
hb_bool_t
hb_feature_from_string (const char *str, int len,
hb_feature_t *feature)
{
hb_feature_t feat;
if (len < 0)
len = strlen (str);
if (likely (parse_one_feature (&str, str + len, &feat)))
{
if (feature)
*feature = feat;
return true;
}
if (feature)
memset (feature, 0, sizeof (*feature));
return false;
}
/**
* hb_feature_to_string:
* @feature: an #hb_feature_t to convert
* @buf: (array length=size) (out): output string
* @size: the allocated size of @buf
*
* Converts a #hb_feature_t into a %NULL-terminated string in the format
* understood by hb_feature_from_string(). The client in responsible for
* allocating big enough size for @buf, 128 bytes is more than enough.
*
* Since: 0.9.5
**/
void
hb_feature_to_string (hb_feature_t *feature,
char *buf, unsigned int size)
{
if (unlikely (!size)) return;
char s[128];
unsigned int len = 0;
if (feature->value == 0)
s[len++] = '-';
hb_tag_to_string (feature->tag, s + len);
len += 4;
while (len && s[len - 1] == ' ')
len--;
if (feature->start != 0 || feature->end != (unsigned int) -1)
{
s[len++] = '[';
if (feature->start)
len += MAX (0, snprintf (s + len, ARRAY_LENGTH (s) - len, "%u", feature->start));
if (feature->end != feature->start + 1) {
s[len++] = ':';
if (feature->end != (unsigned int) -1)
len += MAX (0, snprintf (s + len, ARRAY_LENGTH (s) - len, "%u", feature->end));
}
s[len++] = ']';
}
if (feature->value > 1)
{
s[len++] = '=';
len += MAX (0, snprintf (s + len, ARRAY_LENGTH (s) - len, "%u", feature->value));
}
assert (len < ARRAY_LENGTH (s));
len = MIN (len, size - 1);
memcpy (buf, s, len);
buf[len] = '\0';
}
/* hb_variation_t */
static bool
parse_variation_value (const char **pp, const char *end, hb_variation_t *variation)
{
parse_char (pp, end, '='); /* Optional. */
return parse_float (pp, end, &variation->value);
}
static bool
parse_one_variation (const char **pp, const char *end, hb_variation_t *variation)
{
return parse_tag (pp, end, &variation->tag) &&
parse_variation_value (pp, end, variation) &&
parse_space (pp, end) &&
*pp == end;
}
/**
* hb_variation_from_string:
*
* Since: 1.4.2
*/
hb_bool_t
hb_variation_from_string (const char *str, int len,
hb_variation_t *variation)
{
hb_variation_t var;
if (len < 0)
len = strlen (str);
if (likely (parse_one_variation (&str, str + len, &var)))
{
if (variation)
*variation = var;
return true;
}
if (variation)
memset (variation, 0, sizeof (*variation));
return false;
}
/**
* hb_variation_to_string:
*
* Since: 1.4.2
*/
void
hb_variation_to_string (hb_variation_t *variation,
char *buf, unsigned int size)
{
if (unlikely (!size)) return;
char s[128];
unsigned int len = 0;
hb_tag_to_string (variation->tag, s + len);
len += 4;
while (len && s[len - 1] == ' ')
len--;
s[len++] = '=';
len += MAX (0, snprintf (s + len, ARRAY_LENGTH (s) - len, "%g", variation->value));
assert (len < ARRAY_LENGTH (s));
len = MIN (len, size - 1);
memcpy (buf, s, len);
buf[len] = '\0';
}