![]() ![]() They can be used to check the integrity of a file, download or message, to verify the authenticity of something more precious, such as a passphrase, even for tasks such as testing whether two chunks of text are the same. Exclusive OR the result with the beginning value.There many occasions when we need a ‘fingerprint’ of a file or other data. I needed the crc32 of a file that was pretty large, so I didn't want to read it into memory.įunction _crc32_string ( $text ) )] $part = gmp_xor ( gmp_div_q ( $part, "2" ), $poly64rev ) I made this code to verify Transmition with Vantage Pro2 ( weather station ) based on CRC16-CCITT standard. Print "khash() - maps a crc32 result into a (62-character) result" The khash() function by sukitsupaluk has two problems, it does not use all 62 characters from the $map set and when corrected it then produces different results on 64-bit compared to 32-bit PHP systems. Return the same string as str_pad(dechex(crc32($str)), 8, '0', STR_PAD_LEFT). md5() does) might have been a better plan toįor a more portable solution you may also consider the generic In retrospect having the function return an integer maybe wasn't theīest idea and returning a hex string representation right away (asĮ.g. In about 50% of the cases when moving from 32 to 64bits. Hexadecimal representation seems to be the most common use case weĭecided to not break this even if it breaks direct decimal comparisons Result values was considered but would break the hexadecimal conversionĪs negatives would get an extra 0xFFFFFFFF# offset then. Having 64bit installations also return negative integers for higher Or the dechex() conversion functions, both of theseĪlso take care of converting the crc32() result to ![]() Unsigned crc32() checksum in decimal format.įor a hexadecimal representation of the checksum you can either use the Printf() to get the string representation of the So you need to use the "%u" formatter of sprintf() or On 64bit installationsĪll crc32() results will be positive integers though. Result in negative integers on 32bit platforms. Getting Started Introduction A simple tutorial Language Reference Basic syntax Types Variables Constants Expressions Operators Control Structures Functions Classes and Objects Namespaces Enumerations Errors Exceptions Fibers Generators Attributes References Explained Predefined Variables Predefined Exceptions Predefined Interfaces and Classes Predefined Attributes Context options and parameters Supported Protocols and Wrappers Security Introduction General considerations Installed as CGI binary Installed as an Apache module Session Security Filesystem Security Database Security Error Reporting User Submitted Data Hiding PHP Keeping Current Features HTTP authentication with PHP Cookies Sessions Dealing with XForms Handling file uploads Using remote files Connection handling Persistent Database Connections Command line usage Garbage Collection DTrace Dynamic Tracing Function Reference Affecting PHP's Behaviour Audio Formats Manipulation Authentication Services Command Line Specific Extensions Compression and Archive Extensions Cryptography Extensions Database Extensions Date and Time Related Extensions File System Related Extensions Human Language and Character Encoding Support Image Processing and Generation Mail Related Extensions Mathematical Extensions Non-Text MIME Output Process Control Extensions Other Basic Extensions Other Services Search Engine Extensions Server Specific Extensions Session Extensions Text Processing Variable and Type Related Extensions Web Services Windows Only Extensions XML Manipulation GUI Extensions Keyboard Shortcuts ? This help j Next menu item k Previous menu item g p Previous man page g n Next man page G Scroll to bottom g g Scroll to top g h Goto homepage g s Goto searchīecause PHP's integer type is signed many crc32 checksums will ![]()
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