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Added and updated comments in Java QrSegmentAdvanced.

This commit is contained in:
Project Nayuki 2018-10-03 21:14:45 +00:00
parent 98741eb09a
commit 59e3933e8b
1 changed files with 12 additions and 7 deletions
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19
java/io/nayuki/qrcodegen/QrSegmentAdvanced.java
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@ -37,9 +37,9 @@ public final class QrSegmentAdvanced {
/*---- Optimal list of segments encoder ----*/
/**
* Returns a new mutable list of zero or more segments to represent the specified Unicode text string.
* The resulting list optimally minimizes the total encoded bit length, subjected to the constraints given
* by the specified {error correction level, minimum version number, maximum version number}.
* Returns a list of zero or more segments to represent the specified Unicode text string.
* The resulting list optimally minimizes the total encoded bit length, subjected to the constraints
* in the specified {error correction level, minimum version number, maximum version number}.
* <p>This function can utilize all four text encoding modes: numeric, alphanumeric, byte, and kanji.
* This can be viewed as a significantly more sophisticated and slower replacement for
* {@link QrSegment#makeSegments(String)}, but requiring more input parameters in a way
@ -48,7 +48,7 @@ public final class QrSegmentAdvanced {
* @param ecl the error correction level to use
* @param minVersion the minimum allowed version of the QR symbol (at least 1)
* @param maxVersion the maximum allowed version of the QR symbol (at most 40)
* @return a list of segments containing the text, minimizing the bit length with respect to the constraints
* @return a new mutable list of segments containing the text, minimizing the bit length with respect to the constraints
* @throws NullPointerException if the data or error correction level is {@code null}
* @throws IllegalArgumentException if 1 &le; minVersion &le; maxVersion &le; 40 is violated,
* or if the data is too long to fit in a QR Code at maxVersion at the ECL
@ -87,6 +87,7 @@ public final class QrSegmentAdvanced {
}
// Returns an array representing the optimal mode per code point based on the given text and version.
private static Mode[] computeCharacterModes(int[] codePoints, int version) {
if (codePoints.length == 0)
throw new IllegalArgumentException();
@ -112,16 +113,16 @@ public final class QrSegmentAdvanced {
for (int i = 0; i < codePoints.length; i++) {
int c = codePoints[i];
int[] curCosts = new int[numModes];
{ // Always extend a bytes segment
{ // Always extend a byte mode segment
curCosts[0] = prevCosts[0] + countUtf8Bytes(c) * 8 * 6;
charModes[i][0] = modeTypes[0];
}
// Extend a segment if possible
if (QrSegment.ALPHANUMERIC_CHARSET.indexOf(c) != -1) {
if (QrSegment.ALPHANUMERIC_CHARSET.indexOf(c) != -1) { // Is alphanumeric
curCosts[1] = prevCosts[1] + 33; // 5.5 bits per alphanumeric char
charModes[i][1] = modeTypes[1];
}
if ('0' <= c && c <= '9') {
if ('0' <= c && c <= '9') { // Is numeric
curCosts[2] = prevCosts[2] + 20; // 3.33 bits per digit
charModes[i][2] = modeTypes[2];
}
@ -168,6 +169,8 @@ public final class QrSegmentAdvanced {
}
// Returns a list of segments based on the given text and modes, such that
// consecutive code points in the same mode are put into the same segment.
private static List<QrSegment> splitIntoSegments(int[] codePoints, Mode[] charModes) {
if (codePoints.length == 0)
throw new IllegalArgumentException();
@ -198,6 +201,7 @@ public final class QrSegmentAdvanced {
}
// Returns an array of Unicode code points (effectively UTF-32 / UCS-4) representing the given UTF-16 string.
private static int[] toCodePoints(String s) {
int[] result = s.codePoints().toArray();
for (int c : result) {
@ -208,6 +212,7 @@ public final class QrSegmentAdvanced {
}
// Returns the number of UTF-8 bytes needed to encode the given Unicode code point.
private static int countUtf8Bytes(int cp) {
if (cp < 0) throw new IllegalArgumentException("Invalid code point");
else if (cp < 0x80) return 1;