From fe229628b347baaa4aaa3ddaf574bd313bc184ff Mon Sep 17 00:00:00 2001
From: Stefan `Sec` Zehl <sec@42.org>
Date: Sun, 15 May 2011 22:20:57 +0200
Subject: [PATCH] Debugging tool for fonts. (just checking it in so it doesn't
 get lost)

---
 tools/fdec.c | 170 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 170 insertions(+)
 create mode 100644 tools/fdec.c

diff --git a/tools/fdec.c b/tools/fdec.c
new file mode 100644
index 0000000..7d7f93f
--- /dev/null
+++ b/tools/fdec.c
@@ -0,0 +1,170 @@
+// Demo Compressed font decoder. 
+// Just used for debugging
+// nothing to see, move along...
+// (c) by Sec 5/2011, BSD licence
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define uint8_t unsigned char
+#define uint16_t unsigned short
+
+#include "ubuntu17.c"
+
+const struct FONT_DEF * font = &Font_Ubuntu17pt;
+
+#define MAXCHR (24*3)
+static uint8_t buf[MAXCHR];
+
+int decode(char c){
+	int off=0;				// Offset into au8FontTable for bytestream
+	int length;				// Length of character bytestream
+	int height;				// Height of character in bytes
+	int hoff;
+	uint8_t * bufptr=buf;	// Output buffer for decoded character
+
+	const FONT_CHAR_INFO* fci=font->charInfo;
+
+	// Find offset and length for our character
+	off=0;
+	for(int y=0;y<c-font->u8FirstChar;y++)
+		off+=fci[y].widthBits;
+	length=fci[c-font->u8FirstChar].widthBits;
+
+	height=(font->u8Height-1)/8+1;
+	hoff=font->u8Height%8;
+
+	printf("Doing %c: off=%d, len=%d\n",c,off,length);
+
+	// Local function: Get next nibble.
+	int ctr=0;  // offset for next nibble
+	char gnn(){ // Get next nibble
+		static int byte;
+		static int hilo=0; // 0= high nibble next, 1=low nibble next
+		int val;
+		hilo=1-hilo;
+		if(hilo==1){
+			byte=font->au8FontTable[off+ctr];
+			ctr++;
+			val=byte>>4;
+		}else{
+			val=byte&0x0f;
+		};
+		return val;
+	};
+
+	// Local function: Unpack "long run".
+	int upl(int off){ // unpack "long" run.
+		int retval;
+
+		while((retval=gnn())==0){
+			off++;
+		};
+		while(off-->0){
+//			printf("- rv: %x\n",retval);
+			retval=retval<<4;
+			retval+=gnn();
+		};
+//			printf("> rv: %x\n",retval);
+		return retval;
+	};
+
+
+
+	if(font->au8FontTable[off+0]>>4 == 15){
+		// This is a raw character!
+		int preblank,postblank;
+		const uint8_t *rawptr;
+		preblank=  font->au8FontTable[off+1];
+		postblank= font->au8FontTable[off+2];
+		rawptr=&font->au8FontTable[off+2];
+		printf("Raw character: pre=%d, post=%d\n",preblank,postblank);
+		return;
+	};
+
+
+#define DNY (12)  // Decoder parameter: Fixed value for now.
+	int repeat=0; // Decoder internal: repeat colum?
+	int curbit=0; // Decoder internal: current bit (1 or 0)
+	int pos=0;	  // Decoder internal: current bit position (0..7)
+	int nyb;      // Decoder internal: current nibble / value
+	while(ctr<length){ /* Iterate the whole input stream */
+
+		/* Get next encoded nibble and decode */
+		nyb=gnn();
+		printf("\nCtr: %d, byte: %x, Process: %d\n",ctr, font->au8FontTable[off+ctr], nyb);
+
+		if(nyb==15){
+			repeat++;
+			printf("repeat this line \n");
+			continue;
+		}else if(nyb==14){
+			nyb=upl(0);
+			nyb+=1;
+			printf("14-decode: %d\n",nyb);
+			repeat+=nyb;
+			continue;
+		}else if(nyb>DNY){
+			nyb=(16*(nyb-DNY-1))+gnn()+DNY+1;
+		}else if(nyb==0){
+			nyb=upl(1);
+			nyb+=(16*(13-DNY)+DNY)-16;
+			printf("0-decode: %d\n",nyb);
+		};
+
+		/* Generate & output bits */
+
+		printf("have %d bits. Got %d (%d)-bits...(r=%d)",pos, nyb, curbit,repeat);
+		while(nyb-->0){
+			if(pos==0){
+				*bufptr=0;
+			};
+			if(curbit==1){
+				*bufptr|=1<<(7-pos);
+			};
+			pos++;
+			if( hoff>0 && ((bufptr-buf)%height)==(height-1) && (pos==hoff)){
+				// Incomplete last line.
+				printf("Incomplete last byte output: %d:",(bufptr-buf)%height);
+				pos=8;
+			};
+			if(pos==8 ){
+				printf("BYTE: 0x%02x\n",*bufptr);
+				bufptr++;
+				if((bufptr-buf)%height==0){ // End of column?
+					while(repeat>0){
+						for(int y=0;y<height;y++){
+							bufptr[0]=bufptr[-3];
+							bufptr++;
+						};
+						printf("repeated last line\n");
+						repeat--;
+					};
+				};
+				pos=0;
+				printf("remaining bits: %d\n",nyb);
+			};
+		};
+		curbit=1-curbit;
+	};
+		
+	printf("\n");
+
+	return bufptr-buf;
+};
+
+int main(void){
+
+	int x,sz;
+
+	sz=decode('H');
+	for(x=0;x<sz;x++){
+		printf(" 0x%02x,",buf[x]);
+		if(x%3==2){
+			printf("\n");
+		};
+	};
+
+	exit(0);
+}