From 0eff38ac06adb09fae30528d2687ff813db1d52e Mon Sep 17 00:00:00 2001
From: Stefan `Sec` Zehl <sec@42.org>
Date: Sat, 14 May 2011 22:11:36 +0200
Subject: [PATCH] decode PK-compressed bitmap fonts

---
 lcd/decoder.c | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 lcd/decoder.c

diff --git a/lcd/decoder.c b/lcd/decoder.c
new file mode 100644
index 0000000..7ef07e6
--- /dev/null
+++ b/lcd/decoder.c
@@ -0,0 +1,124 @@
+
+#include <fonts.h>
+#include <render.h>
+
+#define MAXCHR (24*3)
+static uint8_t buf[MAXCHR];
+
+uint8_t * pk_decode(const uint8_t * data,int*len){
+//	int off=0;				// Offset into au8FontTable for bytestream
+	int length=*len;		// Length of character bytestream
+	int height;				// Height of character in bytes
+	uint8_t * bufptr=buf;	// Output buffer for decoded character
+
+	height=(font->u8Height-1)/8+1;
+
+	// Local function: Get next nibble.
+	int ctr=0;  // offset for next nibble
+	int hilo=0; // 0= high nibble next, 1=low nibble next
+	char gnn(){ // Get next nibble
+		static int byte;
+		int val;
+		hilo=1-hilo;
+		if(hilo==1){
+			byte=data[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(data[0]>>4 == 15){
+		// This is a raw character!
+		int preblank,postblank;
+		const uint8_t *rawptr;
+		preblank=  data[1];
+		postblank= data[2];
+		rawptr=&data[3];
+//		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, data[ctr], nyb);
+
+		if(nyb==15){
+			repeat++;
+			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(curbit==1){
+				*bufptr|=1<<(7-pos);
+			}else{
+				*bufptr&=~(1<<(7-pos));
+			};
+			pos++;
+			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;
+			};
+		};
+		curbit=1-curbit;
+	};
+		
+//	printf("\n");
+
+	*len=(bufptr-buf)/height; // return size of output buffer.
+	return buf;
+};