ClientCommon.c   [plain text]


/* -*- Mode: C; tab-width: 4 -*-
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#include <ctype.h>
#include <stdio.h>			// For stdout, stderr

#include "ClientCommon.h"

const char *GetNextLabel(const char *cstr, char label[64])
	{
	char *ptr = label;
	while (*cstr && *cstr != '.')				// While we have characters in the label...
		{
		char c = *cstr++;
		if (c == '\\' && *cstr)					// If we have a backslash, and it's not the last character of the string
			{
			c = *cstr++;
			if (isdigit(cstr[-1]) && isdigit(cstr[0]) && isdigit(cstr[1]))
				{
				int v0 = cstr[-1] - '0';						// then interpret as three-digit decimal
				int v1 = cstr[ 0] - '0';
				int v2 = cstr[ 1] - '0';
				int val = v0 * 100 + v1 * 10 + v2;
				// If valid three-digit decimal value, use it
				// Note that although ascii nuls are possible in DNS labels
				// we're building a C string here so we have no way to represent that
				if (val == 0) val = '-';
				if (val <= 255) { c = (char)val; cstr += 2; }
				}
			}
		*ptr++ = c;
		if (ptr >= label+64) { label[63] = 0; return(NULL); }	// Illegal label more than 63 bytes
		}
	*ptr = 0;													// Null-terminate label text
	if (ptr == label) return(NULL);								// Illegal empty label
	if (*cstr) cstr++;											// Skip over the trailing dot (if present)
	return(cstr);
	}