xref: /netbsd-src/external/apache2/mDNSResponder/dist/Clients/ClientCommon.c (revision a5847cc334d9a7029f6352b847e9e8d71a0f9e0c)
1 /* -*- Mode: C; tab-width: 4 -*-
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39 
40     Change History (most recent first):
41 
42 Log: ClientCommon.c,v $
43 Revision 1.2  2008/05/08 00:42:03  cheshire
44 Removed some unnecessary header files
45 
46 Revision 1.1  2008/05/08 00:25:48  cheshire
47 <rdar://problem/5919272> GetNextLabel insufficiently defensive
48 
49 
50 */
51 
52 #include <ctype.h>
53 #include <stdio.h>			// For stdout, stderr
54 
55 #include "ClientCommon.h"
56 
57 const char *GetNextLabel(const char *cstr, char label[64])
58 	{
59 	char *ptr = label;
60 	while (*cstr && *cstr != '.')				// While we have characters in the label...
61 		{
62 		char c = *cstr++;
63 		if (c == '\\' && *cstr)					// If we have a backslash, and it's not the last character of the string
64 			{
65 			c = *cstr++;
66 			if (isdigit(cstr[-1]) && isdigit(cstr[0]) && isdigit(cstr[1]))
67 				{
68 				int v0 = cstr[-1] - '0';						// then interpret as three-digit decimal
69 				int v1 = cstr[ 0] - '0';
70 				int v2 = cstr[ 1] - '0';
71 				int val = v0 * 100 + v1 * 10 + v2;
72 				// If valid three-digit decimal value, use it
73 				// Note that although ascii nuls are possible in DNS labels
74 				// we're building a C string here so we have no way to represent that
75 				if (val == 0) val = '-';
76 				if (val <= 255) { c = (char)val; cstr += 2; }
77 				}
78 			}
79 		*ptr++ = c;
80 		if (ptr >= label+64) { label[63] = 0; return(NULL); }	// Illegal label more than 63 bytes
81 		}
82 	*ptr = 0;													// Null-terminate label text
83 	if (ptr == label) return(NULL);								// Illegal empty label
84 	if (*cstr) cstr++;											// Skip over the trailing dot (if present)
85 	return(cstr);
86 	}
87