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44 lines
1.2 KiB
C
44 lines
1.2 KiB
C
#include "fmt.h"
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#include "textcode.h"
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size_t fmt_yenc(char* dest,const char* src,size_t len) {
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register const unsigned char* s=(const unsigned char*) src;
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size_t written=0,i;
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int linelen=0;
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for (i=0; i<len; ++i) {
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unsigned char c=s[i]+42;
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switch (c) {
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case ' ': /* escape space at line ending */
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if (linelen==253) {
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if (dest) dest[written]='\n'; ++written; linelen=0;
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}
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goto dontescape;
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case 'F': /* escape "^From " */
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if (s[i+1]+42!='r' || s[i+2]+42!='o' || s[i+3]+42!='m' || s[i+4]+42!=' ') goto dontescape;
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case '.': /* dot at start of line needs to be escaped */
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if (!linelen) goto dontescape;
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/* fall through */
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case 0:
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case '\n':
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case '\r':
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case '=':
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if (dest) dest[written]='='; ++written;
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c+=64;
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/* fall through */
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default:
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dontescape:
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++linelen;
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if (dest) dest[written]=c; ++written;
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if (linelen>253) {
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if (dest) dest[written]='\n'; ++written; linelen=0;
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}
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}
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/* in case someone gives us malicious input */
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if (written>((size_t)-1)/2) return (size_t)-1;
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}
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if (linelen) {
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if (dest) dest[written]='\n'; ++written;
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}
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return written;
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}
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