128 lines
2.6 KiB
C
128 lines
2.6 KiB
C
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#include "fonts.h"
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#include "render.h"
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#include <stdint.h>
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// Local function: Get next nibble.
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static int ctr = 0; // offset for next nibble
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static int hilo = 0; // 0= high nibble next, 1=low nibble next
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static const uint8_t *data;
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#define MAXCHR (30 * 20)
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static uint8_t charBuf[MAXCHR];
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// Get next nibble
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static uint8_t gnn()
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{
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static uint8_t byte;
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uint8_t val;
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if (hilo == 1)
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ctr++;
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hilo = 1 - hilo;
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if (hilo == 1) {
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byte = data[ctr];
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val = byte >> 4;
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} else {
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val = byte & 0x0f;
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};
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return val;
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}
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// Local function: Unpack "long run".
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static int upl(int off)
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{
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int retval;
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while ((retval = gnn()) == 0) {
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off++;
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};
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while (off-- > 0) {
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retval = retval << 4;
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retval += gnn();
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};
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return retval;
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}
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uint8_t *rad1o_pk_decode(const uint8_t *ldata, int *len)
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{
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ctr = 0;
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hilo = 0;
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data = ldata;
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int length = *len; // Length of character bytestream
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int height; // Height of character in bytes
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int hoff; // bit position for non-integer heights
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uint8_t *bufptr = charBuf; // Output buffer for decoded character
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height = (rad1o_getFontHeight() - 1) / 8 + 1;
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hoff = rad1o_getFontHeight() % 8;
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#define DYN (12) // Decoder parameter: Fixed value for now.
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int repeat = 0; // Decoder internal: repeat colum?
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int curbit = 0; // Decoder internal: current bit (1 or 0)
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int pos = 0; // Decoder internal: current bit position (0..7)
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int nyb; // Decoder internal: current nibble / value
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if (data[ctr] >> 4 == 14) { // Char starts with 1-bits.
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gnn();
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curbit = 1;
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};
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while (ctr < length) { /* Iterate the whole input stream */
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/* Get next encoded nibble and decode */
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nyb = gnn();
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if (nyb == 15) {
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repeat++;
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continue;
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} else if (nyb == 14) {
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nyb = upl(0);
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nyb += 1;
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repeat += nyb;
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continue;
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} else if (nyb > DYN) {
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nyb = (16 * (nyb - DYN - 1)) + gnn() + DYN + 1;
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} else if (nyb == 0) {
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nyb = upl(1);
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nyb += (16 * (13 - DYN) + DYN) - 16;
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};
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/* Generate & output bits */
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while (nyb-- > 0) {
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if (pos == 0) // Clear each byte before we start.
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*bufptr = 0;
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if (curbit == 1) {
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*bufptr |= 1 << (7 - pos);
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};
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pos++;
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if (((bufptr - charBuf) % height) == (height - 1) &&
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(pos == hoff)) {
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// Finish incomplete last byte per column
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pos = 8;
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};
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if (pos == 8) {
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bufptr++;
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if ((bufptr - charBuf) % height ==
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0) { // End of column?
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while (repeat > 0) {
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for (int y = 0; y < height;
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y++) {
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bufptr[0] =
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bufptr[-height];
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bufptr++;
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};
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repeat--;
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};
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};
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pos = 0;
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};
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};
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curbit = 1 - curbit;
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};
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*len = (bufptr - charBuf) / height; // return size of output buffer.
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return charBuf;
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}
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