add crctrace

crctrace/Makefile

@@ -0,0 +1,4 @@
+all:
+	gcc -Wall crctrace.c
+	./a.out
+	ruby crctrace.rb

crctrace/crctrace.c

@@ -0,0 +1,43 @@
+#include <stdio.h>
+#include <string.h>
+
+static unsigned short crctracecrc;
+void crctraceout(FILE* fp)
+{
+	fprintf(fp, "%04x\n", crctracecrc);
+}
+
+void crctraceimpl(char* filename, int lineno)
+{
+	unsigned char c = (unsigned char)lineno;
+	unsigned short crc = crctracecrc;
+	int i = 0;
+	int l = strlen(filename);
+	for (; i < l; i++) c ^= filename[i];
+	for (i = 0; i < 8; i++) {
+		unsigned char a = c;
+		if (crc & 1) a++;
+		crc >>= 1;
+		if (a & 1) crc ^= 0xa001;
+		c >>= 1;
+	}
+	crctracecrc = crc;
+}
+#define crctrace() crctraceimpl(__FILE__, __LINE__)
+
+void sub(int i) {
+	crctrace();
+	if (i < 10) {
+		crctrace();
+	}
+}
+
+int main(int argc, char **argv)
+{
+	crctrace();
+	sub(7);
+	crctrace();
+	sub(17);
+	crctraceout(stdout);
+	return 0;
+}

crctrace/crctrace.rb

@@ -0,0 +1,54 @@
+#!/usr/bin/ruby
+def checkpointid(filename, lineno)
+  filename.each_byte.inject(lineno){|a,b|a^b} & 0xff
+end
+
+def crc16(ptn)
+  crc = 0
+  ptn.each do |c|
+    8.times do
+      a = c
+      a += 1 if (crc & 1) == 1
+      crc >>= 1
+      crc ^= 0xa001 if (a & 1) == 1
+      c >>= 1
+    end
+  end
+  crc
+end
+
+files = Dir.glob('*.c')
+checkpoints = {}
+files.each do |filename|
+  body = File.open(filename, 'r'){|fd|fd.read}
+  body.split("\n").each_with_index do |line, l|
+    if /crctrace\(\);/ === line
+      id = checkpointid(filename, l + 1)
+      checkpoints[id] = "#{filename}:#{l + 1}:1:"
+    end
+  end
+end
+
+ucheckpoints = checkpoints.keys.uniq
+if checkpoints.size != ucheckpoints.size
+  puts 'error: not unique'
+  exit
+end
+
+5.times do
+  (1..6).each do |len|
+    u = ucheckpoints * len
+    try = ucheckpoints.size * len * 100
+    try.times do
+      ptn = u.take(len)
+      if crc16(ptn) == 0xfbc3 # TODO
+        puts "found: %s" % ptn.join(', ')
+        ptn.each do |id|
+          puts checkpoints[id]
+        end
+        exit
+      end
+      u.shuffle!
+    end
+  end
+end