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engine: add IPv6 address parsing/printing library from GameNetworkingSockets

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This commit is contained in:
Alibek Omarov 2022-03-11 12:11:25 +03:00
parent 12bfb8f795
commit 193cde83b6
2 changed files with 431 additions and 0 deletions
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377
engine/common/ipv6text.c Normal file
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#include <stdio.h>
#include <string.h>
#include "ipv6text.h"
#ifdef _WIN32
#ifndef snprintf
#define snprintf _snprintf
#endif
#endif
void IPv6IPToString( char *pszOutText, const unsigned char *ip )
{
// Find the longest run of consecutive zero quads.
// If there's a tie, we want the leftmost one.
int idxLongestRunStart = -1;
int nLongestRun = 1; // It must be at least 2 quads in a row, a single 0 must not be compressed
int nCurrentRun = 0;
int idxQuad;
for ( idxQuad = 0 ; idxQuad < 8 ; ++idxQuad )
{
// Zero
if ( ip[idxQuad*2] || ip[idxQuad*2 + 1] )
{
// Terminate run
nCurrentRun = 0;
}
else
{
// Extend (or begin) run
++nCurrentRun;
// Longer than previously found run?
if ( nCurrentRun > nLongestRun )
{
nLongestRun = nCurrentRun;
idxLongestRunStart = idxQuad - nCurrentRun + 1;
}
}
}
// Print the quads
char *p = pszOutText;
idxQuad = 0;
bool bNeedColon = false;
while ( idxQuad < 8 )
{
// Run of compressed zeros?
if ( idxQuad == idxLongestRunStart )
{
*(p++) = ':';
*(p++) = ':';
bNeedColon = false;
idxQuad += nLongestRun;
}
else
{
// Colon to separate from previous, unless
// we are first or immediately follow compressed zero "::"
if ( bNeedColon )
*(p++) = ':';
// Next quad should should print a separator
bNeedColon = true;
// Assemble 16-bit quad value from the two bytes
unsigned quad = ( (unsigned)ip[idxQuad*2] << 8U ) | ip[idxQuad*2 + 1];
// Manually do the hex number formatting.
// Lowercase hex digits, with leading zeros omitted
static const char hexdigits[] = "0123456789abcdef";
if ( quad >= 0x0010 )
{
if ( quad >= 0x0100 )
{
if ( quad >= 0x1000 )
*(p++) = hexdigits[ quad >> 12U ];
*(p++) = hexdigits[ ( quad >> 8U ) & 0xf ];
}
*(p++) = hexdigits[ ( quad >> 4U ) & 0xf ];
}
// Least significant digit, which is always printed
*(p++) = hexdigits[ quad & 0xf ];
// On to the next one
++idxQuad;
}
}
// String terminator
*p = '\0';
}
void IPv6AddrToString( char *pszOutText, const unsigned char *ip, uint16_t port, uint32_t scope )
{
char *p = pszOutText;
// Open bracket
*(p++) = '[';
// Print in the IP
IPv6IPToString( p, ip );
// Find the end of the string
while (*p)
++p;
if ( scope )
{
// And now the scope. Max 32-digit scope number is 10 digits
snprintf( p, 12, "%%%d", scope );
// Find the end of the string
while (*p)
++p;
}
// And now the rest. Max 16-digit port number is 6 digits
snprintf( p, 8, "]:%u", (unsigned int)port );
}
static inline int ParseIPv6Addr_HexDigitVal( char c )
{
if ( c >= '0' && c <= '9' ) return c - '0';
if ( c >= 'a' && c <= 'f' ) return c - ('a' - 0xa);
if ( c >= 'A' && c <= 'F' ) return c - ('A' - 0xa);
return -1;
}
static inline int ParseIPv6Addr_DecimalDigitVal( char c )
{
if ( c >= '0' && c <= '9' ) return c - '0';
return -1;
}
bool ParseIPv6Addr_IsSpace( char c )
{
// Newlines don't count, intentionally
return c == ' ' || c == '\t';
}
bool ParseIPv6Addr( const char *pszText, unsigned char *pOutIP, int *pOutPort, uint32_t *pOutScope )
{
while ( ParseIPv6Addr_IsSpace( *pszText ) )
++pszText;
const char *s = pszText;
// Skip opening bracket, if present
if ( *s == '[' )
{
++s;
while ( ParseIPv6Addr_IsSpace( *s ) )
++s;
}
// Special case for leading "::"
bool bQuadMustFollow = true;
unsigned char *d = pOutIP;
unsigned char *pZeroFill = NULL;
unsigned char *pEndIP = pOutIP + 16;
if ( s[0] == ':' && s[1] == ':' )
{
pZeroFill = d;
s += 2;
bQuadMustFollow = false;
}
// Parse quads until we get to the end
for (;;)
{
// Next thing must be a quad, or end of input. Is it a quad?
int quadDigit = ParseIPv6Addr_HexDigitVal( *s );
if ( quadDigit < 0 )
{
if ( bQuadMustFollow )
return false;
break;
}
// No room for more quads?
if ( d >= pEndIP )
return false;
++s;
int quad = quadDigit;
// Now parse up to three additional characters
quadDigit = ParseIPv6Addr_HexDigitVal( *s );
if ( quadDigit >= 0 )
{
quad = ( quad << 4 ) | quadDigit;
++s;
quadDigit = ParseIPv6Addr_HexDigitVal( *s );
if ( quadDigit >= 0 )
{
quad = ( quad << 4 ) | quadDigit;
++s;
quadDigit = ParseIPv6Addr_HexDigitVal( *s );
if ( quadDigit >= 0 )
{
quad = ( quad << 4 ) | quadDigit;
++s;
}
}
}
// Stash it in the next slot, ignoring for now the issue
// of compressed zeros
*(d++) = (unsigned char)( quad >> 8 );
*(d++) = (unsigned char)quad;
// Only valid character for the IP portion is a colon.
// Anything else ends the IP portion
if ( *s != ':' )
break;
// Compressed zeros?
if ( s[1] == ':' )
{
// Eat '::'
s += 2;
// Can only have one range of compressed zeros
if ( pZeroFill )
return false;
// Remember where to insert the compressed zeros
pZeroFill = d;
// An IP can end with '::'
bQuadMustFollow = false;
}
else
{
// If they have filed the entire IP with no compressed zeros,
// then this is unambiguously a port number. That's not
// necessarily the best style, but it *is* unambiguous
// what it should mean, so let's allow it. If there
// are compressed zeros, then this is ambiguous, and we will
// always interpret it as a quad.
if ( !pZeroFill && d >= pEndIP )
break; // leave ':' as next character, for below
// Eat ':'
++s;
// A single colon must be followed by another quad
bQuadMustFollow = true;
}
}
// End of the IP. Do we have compressed zeros?
if ( pZeroFill )
{
// How many zeros do we need to fill?
intptr_t nZeros = pEndIP - d;
if ( nZeros <= 0 )
return false;
// Shift the quads after the bytes to the end
memmove( pZeroFill+nZeros, pZeroFill, d-pZeroFill );
// And now fill the zeros
memset( pZeroFill, 0, nZeros );
}
else
{
// No compressed zeros. Just make sure we filled the IP exactly
if ( d != pEndIP )
return false;
}
if ( *s == '%' )
{
++s;
// Parse scope number
uint32_t unScope = 0;
int nScopeDigit = ParseIPv6Addr_DecimalDigitVal( *s );
if ( nScopeDigit < 0 )
return false;
unScope = (uint32_t)nScopeDigit;
for (;;)
{
++s;
if ( *s == '\0' || *s == ']' || ParseIPv6Addr_IsSpace( *s ) )
break;
nScopeDigit = ParseIPv6Addr_DecimalDigitVal( *s );
if ( nScopeDigit < 0 )
return false;
unScope = unScope * 10 + nScopeDigit;
}
if ( pOutScope )
*pOutScope = unScope;
}
else
{
if ( pOutScope )
*pOutScope = 0;
}
// If we started with a bracket, then the next character MUST be a bracket.
// (And this is the only circumstance in which a closing bracket would be legal)
if ( *pszText == '[' )
{
while ( ParseIPv6Addr_IsSpace( *s ) )
++s;
if ( *s != ']' )
return false;
++s;
}
// Now we are definitely at the end of the IP. Do we have a port?
// We support all of the syntaxes mentioned in RFC5952 section 6 other
// than the ambiguous case
if ( *s == ':' || *s == '#' || *s == '.' || *s == 'p' || *s == 'P' )
{
++s;
}
else
{
while ( ParseIPv6Addr_IsSpace( *s ) )
++s;
if ( *s == '\0' )
{
// Parsed IP without port OK
if ( pOutPort )
*pOutPort = -1;
return true;
}
if ( strncmp( s, "port", 4 ) == 0 )
{
s += 4;
while ( ParseIPv6Addr_IsSpace( *s ) )
++s;
}
else
{
// Extra stuff after the IP which isn't whitespace or a port
return false;
}
}
// We have a port. If they didn't ask for it, that's considered a parse failure.
if ( !pOutPort )
return false;
// Parse port number
int nPort = ParseIPv6Addr_DecimalDigitVal( *s );
if ( nPort < 0 )
return false;
for (;;)
{
++s;
if ( *s == '\0' || ParseIPv6Addr_IsSpace( *s ) )
break;
int portDigit = ParseIPv6Addr_DecimalDigitVal( *s );
if ( portDigit < 0 )
return false;
nPort = nPort * 10 + portDigit;
if ( nPort > 0xffff )
return false;
}
// Consume trailing whitespace; confirm nothing else in the input
while ( ParseIPv6Addr_IsSpace( *s ) )
++s;
if ( *s != '\0' )
return false;
*pOutPort = nPort;
return true;
}

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/// Standalone plain C utilities for parsing and printing IPv6 addresses
#pragma once
#include <stdint.h>
#include <stdbool.h>
/// Max length of an IPv6 string, with scope, WITHOUT port number, including \0':
/// 0123:4567:89ab:cdef:0123:4567:89ab:cdef%4294967295
#define k_ncchMaxIPV6AddrStringWithoutPort 51;
/// Max number of bytes output by IPv6AddrToString, including '\0':
/// [0123:4567:89ab:cdef:0123:4567:89ab:cdef%4294967295]:12345
/// There are other strings that are acceptable to ParseIPv6Addr
/// that are longer than this, but this is the longest canonical
/// string.
#define k_ncchMaxIPV6AddrStringWithPort 59;
#ifdef __cplusplus
extern "C" {
#endif
/// Format an IPv6 address to the canonical form according to RFC5952.
/// The address should be 16 bytes (e.g. same as in6_addr::s6_addr).
/// Your buffer MUST be at least k_ncchMaxIPV6AddrStringWithoutPort bytes.
extern void IPv6IPToString( char *pszOutText, const unsigned char *ip );
/// Format IPv6 IP and port to string. This uses the recommended
/// bracket notation, eg [1234::1]:12345. Your buffer must be
/// at least k_ncchMaxIPV6AddrStringWithPort bytes.
extern void IPv6AddrToString( char *pszOutText, const unsigned char *ip, uint16_t port, uint32_t scope );
/// Parse IPv6 address string. Returns true if parsed OK. Returns false
/// if input cannot be parsed, or if input specifies a port but pOutPort is NULL.
/// If input does not specify a port, and pOutPort is non-NULL, then *pOutPort is
/// set to -1.
///
/// Parsing is tolerant of any unambiguous IPv6 representation, the input
/// need not be the canonical RFC5952 representation.
///
/// IPv6 zones are not supported.
///
/// Leading and trailing whitespace is OK around the entire string,
/// but not internal whitespace. The different methods for separating the
/// port in RFC5952 are supported section 6, except the ambiguous case
/// of a colon to separate the port, when the IP contains a double-colon.
/// Brackets around an IP are OK, even if there is no port.
///
/// Address must point to a 16-byte buffer (e.g. same as in6_addr::s6_addr)
/// Port is returned in host byte order.
extern bool ParseIPv6Addr( const char *pszText, unsigned char *pOutIP, int *pOutPort, uint32_t *pOutScope );
#ifdef __cplusplus
}
#endif