Add importing of single page .t42 files, wrt #2
This commit is contained in:
G.K.MacGregor
190
loadsave.cpp
190
loadsave.cpp
@@ -26,6 +26,7 @@
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#include <QTextStream>
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#include "document.h"
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#include "hamming.h"
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#include "levelonepage.h"
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#include "pagebase.h"
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@@ -166,6 +167,195 @@ void loadTTI(QFile *inFile, TeletextDocument *document)
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}
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}
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void importT42(QFile *inFile, TeletextDocument *document)
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{
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unsigned char inLine[42];
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int readMagazineNumber, readPacketNumber;
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int foundMagazineNumber = -1;
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int foundPageNumber = -1;
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bool firstPacket0Found = false;
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bool pageBodyPacketsFound = false;
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for (;;) {
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if (inFile->read((char *)inLine, 42) != 42)
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// Reached end of .t42 file, or less than 42 bytes left
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break;
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// Magazine and packet numbers
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inLine[0] = hamming_8_4_decode[inLine[0]];
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inLine[1] = hamming_8_4_decode[inLine[1]];
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if (inLine[0] == 0xff || inLine[1] == 0xff)
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// Error decoding magazine or packet number
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continue;
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readMagazineNumber = inLine[0] & 0x07;
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readPacketNumber = (inLine[0] >> 3) | (inLine[1] << 1);
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if (readPacketNumber == 0) {
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// Hamming decode page number, subcodes and control bits
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for (int i=2; i<10; i++)
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inLine[i] = hamming_8_4_decode[inLine[i]];
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// See if the page number is valid
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if (inLine[2] == 0xff || inLine[3] == 0xff)
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// Error decoding page number
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continue;
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const int readPageNumber = (inLine[3] << 4) | inLine[2];
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if (readPageNumber == 0xff)
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// Time filling header
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continue;
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// A second or subsequent X/0 has been found
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if (firstPacket0Found) {
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if (readMagazineNumber != foundMagazineNumber)
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// Packet from different magazine broadcast in parallel mode
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continue;
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if ((readPageNumber == foundPageNumber) && pageBodyPacketsFound)
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// X/0 with same page number found after page body packets loaded - assume end of page
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break;
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if (readPageNumber != foundPageNumber) {
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// More than one page in .t42 file - end of current page reached
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qDebug("More than one page in .t42 file");
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break;
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}
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// Could get here if X/0 with same page number was found with no body packets inbetween
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continue;
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} else {
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// First X/0 found
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foundMagazineNumber = readMagazineNumber;
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foundPageNumber = readPageNumber;
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firstPacket0Found = true;
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document->setPageNumber((foundMagazineNumber << 8) | foundPageNumber);
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document->subPage(0)->setControlBit(PageBase::C4ErasePage, inLine[5] & 0x08);
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document->subPage(0)->setControlBit(PageBase::C5Newsflash, inLine[7] & 0x04);
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document->subPage(0)->setControlBit(PageBase::C6Subtitle, inLine[7] & 0x08);
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for (int i=0; i<4; i++)
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document->subPage(0)->setControlBit(PageBase::C7SuppressHeader+i, inLine[8] & (1 << i));
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document->subPage(0)->setControlBit(PageBase::C11SerialMagazine, inLine[9] & 0x01);
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document->subPage(0)->setControlBit(PageBase::C12NOS, inLine[9] & 0x08);
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document->subPage(0)->setControlBit(PageBase::C13NOS, inLine[9] & 0x04);
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document->subPage(0)->setControlBit(PageBase::C14NOS, inLine[9] & 0x02);
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continue;
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}
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}
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// No X/0 has been found yet, keep looking for one
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if (!firstPacket0Found)
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continue;
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// Disregard whole-magazine packets
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if (readPacketNumber > 28)
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continue;
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// We get here when a page-body packet belonging to the found X/0 header was found
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pageBodyPacketsFound = true;
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// At the moment this only loads a Level One Page properly
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// because it assumes X/1 to X/25 is odd partity
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if (readPacketNumber < 25) {
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for (int i=2; i<42; i++)
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// TODO - obey odd parity?
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inLine[i] &= 0x7f;
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document->subPage(0)->setPacket(readPacketNumber, QByteArray((const char *)&inLine[2], 40));
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continue;
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}
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// X/26, X/27 or X/28
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int readDesignationCode = hamming_8_4_decode[inLine[2]];
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if (readDesignationCode == 0xff)
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// Error decoding designation code
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continue;
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if (readPacketNumber == 27 && readDesignationCode < 4) {
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// X/27/0 to X/27/3 for Editorial Linking
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// Decode Hamming 8/4 on each of the six links, checking for errors on the way
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for (int i=0; i<6; i++) {
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bool decodingError = false;
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const int b = 3 + i*6; // First byte of this link
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for (int j=0; j<6; j++) {
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inLine[b+j] = hamming_8_4_decode[inLine[b+j]];
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if (inLine[b+j] == 0xff) {
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decodingError = true;
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break;
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}
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}
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if (decodingError) {
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// Error found in at least one byte of the link
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// Neutralise the whole link to same magazine, page FF, subcode 3F7F
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qDebug("X/27/%d link %d decoding error", readDesignationCode, i);
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inLine[b] = 0xf;
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inLine[b+1] = 0xf;
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inLine[b+2] = 0xf;
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inLine[b+3] = 0x7;
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inLine[b+4] = 0xf;
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inLine[b+5] = 0x3;
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}
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}
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document->subPage(0)->setPacket(readPacketNumber, readDesignationCode, QByteArray((const char *)&inLine[2], 40));
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continue;
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}
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// X/26, or X/27/4 to X/27/15, or X/28
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// Decode Hamming 24/18
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for (int i=0; i<13; i++) {
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const int b = 3 + i*3; // First byte of triplet
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const int p0 = inLine[b];
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const int p1 = inLine[b+1];
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const int p2 = inLine[b+2];
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unsigned int D1_D4;
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unsigned int D5_D11;
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unsigned int D12_D18;
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unsigned int ABCDEF;
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int32_t d;
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D1_D4 = hamming_24_18_decode_d1_d4[p0 >> 2];
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D5_D11 = p1 & 0x7f;
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D12_D18 = p2 & 0x7f;
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d = D1_D4 | (D5_D11 << 4) | (D12_D18 << 11);
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ABCDEF = (hamming_24_18_parities[0][p0] ^ hamming_24_18_parities[1][p1] ^ hamming_24_18_parities[2][p2]);
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d ^= (int)hamming_24_18_decode_correct[ABCDEF];
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if ((d & 0x80000000) == 0x80000000) {
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// Error decoding Hamming 24/18
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qDebug("X/%d/%d triplet %d decoding error", readPacketNumber, readDesignationCode, i);
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if (readPacketNumber == 26) {
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// Enhancements packet, set to "dummy" Address 41, Mode 0x1e, Data 0
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inLine[b] = 41;
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inLine[b+1] = 0x1e;
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inLine[b+2] = 0;
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} else {
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// Zero out whole decoded triplet, bound to make things go wrong...
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inLine[b] = 0x00;
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inLine[b+1] = 0x00;
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inLine[b+2] = 0x00;
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}
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} else {
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inLine[b] = d & 0x0003f;
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inLine[b+1] = (d & 0x00fc0) >> 6;
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inLine[b+2] = d >> 12;
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}
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}
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document->subPage(0)->setPacket(readPacketNumber, readDesignationCode, QByteArray((const char *)&inLine[2], 40));
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}
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if (!firstPacket0Found)
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qDebug("No X/0 found");
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else if (!pageBodyPacketsFound)
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qDebug("X/0 found, but no page body packets were found");
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}
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// Used by saveTTI and HashString
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int controlBitsToPS(PageBase *subPage)
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{
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