yenc reconstruction feature for uudecode

CHANGES

@@ -2,6 +2,7 @@
   man page update (document stralloc return values)
   add stralloc_chop and stralloc_chomp
   add buffer_putsa, buffer_get_token_sa and buffer_getline_sa
+  extended uudecode test.  See comment at top for details.
 
 0.14:
   avoid bus errors in byte_copy

test/uudecode.c

@@ -1,9 +1,80 @@
+/* this is a uudecode that also handles yenc encoded data.  The encoded
+ * messages are read from stdin.  The yenc decoder even tries to
+ * reconstruct mutilated encodings.  One of my news servers has the
+ * problem that it gets corrupted yenc data through one of the uplinks
+ * that replace "^." with "^..".  This decoder will try reversing this
+ * when decoding a part with broken crc. */
 #include <unistd.h>
 #include <stdlib.h>
 #include "textcode.h"
 #include "str.h"
 #include "buffer.h"
 #include "open.h"
+#include "stralloc.h"
+
+static const uint32_t crc_table[256] = {
+  0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
+  0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
+  0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
+  0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
+  0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
+  0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
+  0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
+  0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
+  0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
+  0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
+  0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
+  0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
+  0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
+  0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
+  0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
+  0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
+  0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
+  0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
+  0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
+  0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
+  0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
+  0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
+  0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
+  0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
+  0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
+  0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
+  0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
+  0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
+  0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
+  0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
+  0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
+  0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
+  0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
+  0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
+  0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
+  0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
+  0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
+  0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
+  0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
+  0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
+  0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
+  0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
+  0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
+  0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
+  0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
+  0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
+  0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
+  0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
+  0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
+  0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
+  0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
+  0x2d02ef8dL
+};
+
+unsigned int crc32(unsigned int crc, const char* buf, unsigned int len) {
+  crc = crc ^ 0xffffffffL;
+  while (len) {
+    crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
+    --len;
+  }
+  return crc ^ 0xffffffffL;
+}
 
 int main(int argc,char* argv[]) {
   char buf[4096];
@@ -19,7 +90,9 @@ int main(int argc,char* argv[]) {
   enum { BEFOREBEGIN, AFTERBEGIN, SKIPHEADER } state=BEFOREBEGIN;
   enum { UUDECODE, YENC } mode=UUDECODE;
   unsigned long fmode=0,lineno=0;
-  unsigned long offset,endoffset,totalsize,linelen; /* used only for yenc */
+  unsigned long offset,endoffset,totalsize,linelen,part,warned; /* used only for yenc */
+  static stralloc yencpart;
+  unsigned int crc;
 
   if (argc>1) {
     fd=open_read(argv[1]);
@@ -88,9 +161,12 @@ foundfilename:
 	    buffer_puts(buffer_2,line+l);
 	    buffer_putsflush(buffer_2,"\" (must not exist yet)\n");
 	  } else {
+	    if (mode!=YENC || part==1) {
 	      buffer_puts(buffer_2,"decoding file \"");
 	      buffer_puts(buffer_2,line+l);
 	      buffer_putsflush(buffer_2,"\"\n");
+	      warned=0;
+	    }
 	    state=AFTERBEGIN;
 	    buffer_init(&fileout,write,ofd,obuf,sizeof obuf);
 	    continue;
@@ -117,11 +193,14 @@ invalidybegin:
 	continue;
       }
       l=filename-line+6;
+      if (!(filename=strstr(line," part="))) goto invalidybegin;
+      if (filename[6+scan_ulong(filename+6,&part)] != ' ') goto invalidybegin;
       if (!(filename=strstr(line," size="))) goto invalidybegin;
       if (filename[6+scan_ulong(filename+6,&totalsize)] != ' ') goto invalidybegin;
       if (!(filename=strstr(line," line="))) goto invalidybegin;
       if (filename[6+scan_ulong(filename+6,&linelen)] != ' ') goto invalidybegin;
       mode=YENC;
+      stralloc_copys(&yencpart,""); crc=0;
       goto foundfilename;
     } else if (str_start(line,"=ypart ")) {
       char* tmp=strstr(line," begin=");
@@ -143,6 +222,54 @@ invalidpart:
       lseek(ofd,offset,SEEK_SET);
       continue;
     } else if (str_start(line,"=yend")) {
+      /* first try to decode it normally and see if the CRC matches */
+      unsigned long i,wantedcrc;
+      stralloc out;
+      char* tmp=strstr(line," pcrc32=");
+
+      if (!tmp) goto invalidpart;
+      if (!scan_xlong(tmp+8,&wantedcrc))
+	goto invalidpart;
+      stralloc_init(&out);
+      stralloc_0(&yencpart);
+      stralloc_ready(&out,yencpart.len);
+      for (i=0; i<yencpart.len; ) {
+	unsigned int x,scanned;
+	x=scan_yenc(yencpart.s+i,out.s+out.len,&scanned);
+	i+=x+1; out.len+=scanned;
+      }
+      i=crc32(0,out.s,out.len);
+      if (out.len == endoffset-offset && i == wantedcrc) {
+	/* ok, save block */
+	buffer_put(&fileout,out.s,out.len);
+      } else {
+	if (warned==0) {
+	  buffer_puts(buffer_2,"warning: corrupt yenc part; expected crc ");
+	  buffer_putxlong(buffer_2,wantedcrc);
+	  buffer_puts(buffer_2,", got crc ");
+	  buffer_putxlong(buffer_2,i);
+	  buffer_putsflush(buffer_2,"; attempting reconstruction... ");
+	}
+	out.len=0;
+	for (i=0; i<yencpart.len; ) {
+	  unsigned int x,scanned;
+	  if (yencpart.s[i]=='.' && yencpart.s[i+1]=='.') ++i;
+	  x=scan_yenc(yencpart.s+i,out.s+out.len,&scanned);
+	  i+=x+1; out.len+=scanned;
+	}
+	i=crc32(0,out.s,out.len);
+	if (out.len == endoffset-offset && i == wantedcrc) {
+	  if (!warned) buffer_putsflush(buffer_2,"success!\n");
+	  buffer_put(&fileout,out.s,out.len);
+	} else
+	  buffer_putsflush(buffer_2,"\nerror: unable to compensate for broken yenc part!\n");
+	warned=1;
+      }
+      stralloc_free(&out);
+      buffer_flush(&fileout);
+      close(ofd);
+      ofd=-1;
+#if 0
       unsigned long cur;
       if (ofd>=0) {
 	off_t rlen;
@@ -159,6 +286,7 @@ invalidpart:
 	close(ofd);
 	ofd=-1;
       }
+#endif
       ++found;
       state=BEFOREBEGIN;
       continue;
@@ -171,6 +299,10 @@ invalidpart:
       switch (mode) {
       case UUDECODE: x=scan_uuencoded(line,tmp,&scanned); break;
       case YENC:
+	stralloc_cats(&yencpart,line);
+	stralloc_cats(&yencpart,"\n");
+	continue;
+#if 0
 	/* work around broken yenc encoders */
 	if ((line[0]=='.' && line[1]=='.') ||
 	    (line[0]=='>' && line[1]=='.')) {
@@ -185,6 +317,7 @@ invalidpart:
 	}
 	x=scan_yenc(line,tmp,&scanned);
 	break;
+#endif
       }
       if (!x) {
 	if (state==AFTERBEGIN) {
@@ -202,3 +335,5 @@ invalidpart:
     }
   }
 }
+
+