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libphutil/src/xsprintf/xsprintf.php
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xsprintf.php
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<?php
/*
* Copyright 2012 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/**
* Parse a sprintf()-style format string in an extensible way.
*
* This method allows you to build a function with sprintf() semantics but
* custom conversions for different datatypes. Three examples are
* @{function:jsprintf} (which builds Javascript strings),
* @{function:qsprintf} (which builds MySQL strings), and
* @{function:csprintf} (which builds command line strings).
*
* To build a new xsprintf-family function, provide a callback which conforms
* to the specification described in @{function:xsprintf_callback_example}. The
* callback will be invoked each time a conversion (like "%Z") is encountered
* in the string. For instance, if you call xsprintf() like this...
*
* $result = xsprintf(
* 'xsprintf_callback_example',
* $userdata = null,
* array(
* "The %M is made of %C.",
* 'moon',
* 'cheese',
* ));
*
* ...the callback will be invoked twice, at string positions 5 ("M") and 19
* ("C"), with values "moon" and "cheese" respectively.
*
* @param string The name of a callback to pass conversions to.
* @param wild Optional userdata to pass to the callback. For
* @{function:qsprintf}, this is the database connection.
* @param list List of arguments, with the sprintf() pattern in position 0.
* @return string Formatted string.
*
* @group util
*/
function xsprintf($callback, $userdata, $argv) {
$argc = count($argv);
$arg = 0;
$pos = 0;
$pattern = $argv[0];
$len = strlen($pattern);
$conv = false; // Are we inside a conversion?
for ($pos = 0; $pos < $len; $pos++) {
$c = $pattern[$pos];
if ($conv) {
// We could make a greater effort to support formatting modifiers,
// but they really have no place in semantic string formatting.
if (strpos("'-0123456789.\$+", $c) !== false) {
throw new Exception(
"xsprintf() does not support the `%{$c}' modifier.");
}
if ($c != '%') {
$conv = false;
$arg++;
if ($arg >= $argc) {
throw new Exception("Too few arguments to xsprintf().");
}
$callback($userdata, $pattern, $pos, $argv[$arg], $len);
}
}
if ($c == '%') {
// If we have "%%", this encodes a literal percentage symbol, so we are
// no longer inside a conversion.
$conv = !$conv;
}
}
if ($arg != ($argc - 1)) {
throw new Exception("Too many arguments to xsprintf().");
}
$argv[0] = $pattern;
return call_user_func_array('sprintf', $argv);
}
/**
* Example @{function:xsprintf} callback. When you call xsprintf(), you
* must pass a callback like this one. xsprintf() will invoke the callback when
* it encounters a conversion (like "%Z") in the pattern string.
*
* Generally, this callback should examine ##$pattern[$pos]## (which will
* contain the conversion character, like 'Z'), escape ##$value## appropriately,
* and then replace ##$pattern[$pos]## with an 's' so sprintf() prints the
* escaped value as a string. However, more sophisticated behaviors are possible
* -- particularly, consuming multiple characters to allow for conversions like
* "%Ld". In this case, the callback needs to substr_replace() the entire
* conversion with 's' and then update ##$length##.
*
* For example implementations, see @{function:xsprintf_command},
* @{function:xsprintf_javascript},
* and @{function:xsprintf_query}.
*
* @param wild Arbitrary, optional userdata. This is whatever userdata
* was passed to @{function:xsprintf}.
* @param string The pattern string being parsed.
* @param int The current character position in the string.
* @param wild The value to convert.
* @param int The string length.
*
* @group util
*/
function xsprintf_callback_example(
$userdata,
&$pattern,
&$pos,
&$value,
&$length) {
throw new Exception(
"This function exists only to document the call signature for xsprintf() ".
"callbacks.");
}
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