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Add methods allowing masking of Strings #332

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902b761
Add methods allowing masking of Strings
greenman18523 Jun 2, 2018
4c972e1
Add method that mask in the middle and allows unmasked from both sides
greenman18523 Jul 6, 2018
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178 changes: 178 additions & 0 deletions src/main/java/org/apache/commons/lang3/StringUtils.java
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Original file line number Diff line number Diff line change
Expand Up @@ -9341,4 +9341,182 @@ public static int[] toCodePoints(final CharSequence str) {
}
return result;
}

/**
* <p>Masks the given {@code str} by replacing, starting from the first character of the {@link String}, at list
* {@code minMasked} characters.</p>
*
* <p>The result will have up to the last {@code maxUnmasked} characters with the same value as the original
* {@code str} with the rest being replaced by {@code mask}.</p>
*
* <p>For {@code null} or {@link String#isEmpty() empty} {@code str}, the same {@link String} is returned.</p>
*
* <p>Negative values for {@code minMasked} and {@code maxUnmasked} are set to zero.</p>
*
* <pre>
* StringUtils.maskStart(null, *, *, *) = null
* StringUtils.maskStart("", *, *, *) = ""
* StringUtils.maskStart("test", *, -1, 4) = "test"
* StringUtils.maskStart("test", *, 0, 4) = "test"
* StringUtils.maskStart("test", 'X', 1, 4) = "Xest"
* StringUtils.maskStart("test", 'X', 1, 2) = "XXst"
* StringUtils.maskStart("test", 'X', 1, -1) = "XXXX"
* StringUtils.maskStart("test", 'X', 1, 0) = "XXXX"
* </pre>
*
* <p>This is equivalent to calling {@code mask(str, mask, minMasked, 0, maxUnmasked)}</p>
*
* @param str the String to mask it's content
* @param mask the character used as the mask
* @param minMasked the minimum number of characters to mask
* @param maxUnmasked the maximum number of characters that will remain unmasked
*
* @return the masked String
*
* @see #mask(String, char, int, int, int)
* @see #maskEnd(String, char, int, int)
*
* @since 3.8
*/
public static String maskStart(final String str, final char mask, int minMasked, int maxUnmasked) {
return mask(str, mask, minMasked, 0, maxUnmasked);
}

/**
* <p>Masks the given {@code str} by replacing, starting from the last character of the {@link String}, at list
* {@code minMasked} characters.</p>
*
* <p>The result will have up to the first {@code maxUnmasked} characters with the same value as the original
* {@code str} with the rest being replaced by {@code mask}.</p>
*
* <p>For {@code null} or {@link String#isEmpty() empty} {@code str}, the same {@link String} is returned.</p>
*
* <p>Negative values for {@code minMasked} and {@code maxUnmasked} are set to zero.</p>
*
* <pre>
* StringUtils.maskEnd(null, *, *, *) = null
* StringUtils.maskEnd("", *, *, *) = ""
* StringUtils.maskEnd("test", *, -1, 4) = "test"
* StringUtils.maskEnd("test", *, 0, 4) = "test"
* StringUtils.maskEnd("test", 'X', 1, 4) = "tesX"
* StringUtils.maskEnd("test", 'X', 1, 2) = "teXX"
* StringUtils.maskEnd("test", 'X', 1, -1) = "XXXX"
* StringUtils.maskEnd("test", 'X', 1, 0) = "XXXX"
* </pre>
*
* <p>This is equivalent to calling {@code mask(str, mask, minMasked, maxUnmasked, 0)}</p>
*
* @param str the String to mask it's content
* @param mask the character used as the mask
* @param minMasked the minimum number of characters to mask
* @param maxUnmasked the maximum number of characters that will remain unmasked
*
* @return the masked String
*
* @see #mask(String, char, int, int, int)
* @see #maskStart(String, char, int, int)
*
* @since 3.8
*/
public static String maskEnd(final String str, final char mask, int minMasked, int maxUnmasked) {
return mask(str, mask, minMasked, maxUnmasked, 0);
}

/**
* <p>Masks the given {@code str} by replacing at list {@code minMasked} characters.</p>
*
* <p>The result will have up to {@code maxUnmaskedStart} + {@code maxUnmaskedEnd} characters with the same value as
* the original {@code str} with the rest being replaced by {@code mask}.</p>
*
* <p>For {@code null} or {@link String#isEmpty() empty} {@code str}, the same {@link String} is returned.</p>
*
* <p>Negative values for {@code minMasked}, {@code maxUnmaskedStart} and {@code maxUnmaskedEnd} are set to zero.</p>
*
* <pre>
* StringUtils.maskStart(null, *, *, *, *) = null
* StringUtils.maskStart("", *, *, *, *) = ""
* StringUtils.maskStart("test", *, -1, 2, 2) = "test"
* StringUtils.maskStart("test", *, 0, 2, 2) = "test"
* StringUtils.maskStart("test", *, 4, *, *) = "XXXX"
* StringUtils.maskStart("test", *, 0, 2, 2) = "test"
* StringUtils.maskStart("test", *, 1, 2, 2) = "tXst"
* StringUtils.maskStart("test", *, 2, 2, 2) = "tXXt"
* StringUtils.maskStart("test", *, 1, 1, 1) = "tXXt"
* StringUtils.maskStart("test", *, 1, 2, 1) = "teXt"
* StringUtils.maskStart("test", *, 1, 1, 2) = "tXst"
* </pre>
*
* @param str the String to mask it's content
* @param mask the character used as the mask
* @param minMasked the minimum number of characters to mask
* @param maxUnmaskedStart the maximum number of characters that will remain unmasked from the start
* @param maxUnmaskedEnd the maximum number of characters that will remain unmasked from the end
*
* @return the masked String
*
* @see #maskStart(String, char, int, int)
* @see #maskEnd(String, char, int, int)
*
* @since 3.8
*/
public static String mask(final String str, final char mask, int minMasked, int maxUnmaskedStart, int maxUnmaskedEnd) {
if (isEmpty(str)) {
//Nothing to mask
return str;
}
if (minMasked < 0) {
minMasked = 0;
}
if (maxUnmaskedStart < 0) {
maxUnmaskedStart = 0;
}
if (maxUnmaskedEnd < 0) {
maxUnmaskedEnd = 0;
}

final int strLength = str.length();
final int maskLength;
final int maskStart;
if (strLength <= minMasked) {
maskLength = strLength;
maskStart = 0;
} else if ((long)strLength < (long)minMasked + maxUnmaskedStart + maxUnmaskedEnd) {
//long to avoid int overflow
maskLength = minMasked;
int diff = Math.abs(maxUnmaskedStart - maxUnmaskedEnd);
if (diff == 0) {
maxUnmaskedStart = (strLength - minMasked)/2;
} else {
int remainingChars = strLength - maskLength;
if (diff > remainingChars) {
if (maxUnmaskedStart > maxUnmaskedEnd) {
maxUnmaskedStart = remainingChars;
} else {
maxUnmaskedStart = 0;
}
} else {
if (maxUnmaskedStart > maxUnmaskedEnd) {
maxUnmaskedStart = remainingChars - diff;
} else {
maxUnmaskedStart = diff;
}
}
}

maskStart = maxUnmaskedStart;
} else {
maskLength = strLength - maxUnmaskedStart - maxUnmaskedEnd;
maskStart = maxUnmaskedStart;
}

if (maskLength == 0) {
//Fast path, no need to mask
return str;
}

final char[] values = str.toCharArray();
Arrays.fill(values, maskStart, maskStart+ maskLength, mask);

return new String(values);
}
}
73 changes: 73 additions & 0 deletions src/test/java/org/apache/commons/lang3/StringUtilsTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -3277,4 +3277,77 @@ public void testGetDigits() {
assertEquals("5417543010", StringUtils.getDigits("(541) 754-3010"));
assertEquals("\u0967\u0968\u0969", StringUtils.getDigits("\u0967\u0968\u0969"));
}

@Test
public void testMaskStart() {
assertNull(StringUtils.maskStart(null, 'a', 0, 0));
assertEquals("", StringUtils.maskStart("", 'a', 0, 0));
assertEquals("test", StringUtils.maskStart("test", 'X', -1, 4));
assertEquals("XXXX", StringUtils.maskStart("test", 'X', 0, -1));
assertEquals("test", StringUtils.maskStart("test", 'X', 0, 4));
assertEquals("Xest", StringUtils.maskStart("test", 'X', 0, 3));
assertEquals("XXst", StringUtils.maskStart("test", 'X', 0, 2));
assertEquals("XXXt", StringUtils.maskStart("test", 'X', 0, 1));
assertEquals("XXXX", StringUtils.maskStart("test", 'X', 0, 0));
assertEquals("Xest", StringUtils.maskStart("test", 'X', 1, 4));
assertEquals("XXst", StringUtils.maskStart("test", 'X', 2, 4));
assertEquals("XXXt", StringUtils.maskStart("test", 'X', 3, 4));
assertEquals("XXXX", StringUtils.maskStart("test", 'X', 4, 4));

assertEquals("Xest", StringUtils.maskStart("test", 'X', 1, Integer.MAX_VALUE));
assertEquals("XXXX", StringUtils.maskStart("test", 'X', 1, Integer.MIN_VALUE));
}

@Test
public void testMaskEnd() {
assertNull(StringUtils.maskEnd(null, 'a', 0, 0));
assertEquals("", StringUtils.maskEnd("", 'a', 0, 0));
assertEquals("test", StringUtils.maskEnd("test", 'X', -1, 4));
assertEquals("XXXX", StringUtils.maskEnd("test", 'X', 0, -1));
assertEquals("test", StringUtils.maskEnd("test", 'X', 0, 4));
assertEquals("tesX", StringUtils.maskEnd("test", 'X', 0, 3));
assertEquals("teXX", StringUtils.maskEnd("test", 'X', 0, 2));
assertEquals("tXXX", StringUtils.maskEnd("test", 'X', 0, 1));
assertEquals("XXXX", StringUtils.maskEnd("test", 'X', 0, 0));
assertEquals("tesX", StringUtils.maskEnd("test", 'X', 1, 4));
assertEquals("teXX", StringUtils.maskEnd("test", 'X', 2, 4));
assertEquals("tXXX", StringUtils.maskEnd("test", 'X', 3, 4));
assertEquals("XXXX", StringUtils.maskEnd("test", 'X', 4, 4));

assertEquals("tesX", StringUtils.maskEnd("test", 'X', 1, Integer.MAX_VALUE));
assertEquals("XXXX", StringUtils.maskEnd("test", 'X', 1, Integer.MIN_VALUE));
}

@Test
public void testMask() {
assertNull(StringUtils.mask(null, '*', 4, 4, 4 ));
assertEquals("", StringUtils.mask("", '*', 4, 4, 4));
assertEquals("test", StringUtils.mask("test", 'X', -1, 2, 2));
assertEquals("XXXX", StringUtils.mask("test", 'X', 0, -1, -1));
assertEquals("test", StringUtils.mask("test", 'X', 0, 2, 2));
assertEquals("tesX", StringUtils.mask("test", 'X', 0, 3, 0));
assertEquals("teXX", StringUtils.mask("test", 'X', 0, 2, 0));
assertEquals("tXXX", StringUtils.mask("test", 'X', 0, 1, 0));
assertEquals("XXXX", StringUtils.mask("test", 'X', 0, 0, 0));

assertEquals("Xest", StringUtils.mask("test", 'X', 0, 0, 3));
assertEquals("XXst", StringUtils.mask("test", 'X', 0, 0, 2));
assertEquals("XXXt", StringUtils.mask("test", 'X', 0, 0, 1));

assertEquals("tXst", StringUtils.mask("test", 'X', 1, 4, 4));
assertEquals("tXXt", StringUtils.mask("test", 'X', 2, 4, 4));
assertEquals("XXXt", StringUtils.mask("test", 'X', 3, 4, 4));
assertEquals("XXXX", StringUtils.mask("test", 'X', 4, 4, 4));

assertEquals("tXst", StringUtils.mask("test", 'X', 1, Integer.MAX_VALUE, Integer.MAX_VALUE));
assertEquals("teXst", StringUtils.mask("teest", 'X', 1, Integer.MAX_VALUE, Integer.MAX_VALUE));
assertEquals("tesX", StringUtils.mask("test", 'X', 1, Integer.MAX_VALUE, 0));
assertEquals("Xest", StringUtils.mask("test", 'X', 1, 0, Integer.MAX_VALUE));
assertEquals("Xest", StringUtils.mask("test", 'X', 1, Integer.MAX_VALUE - 5, Integer.MAX_VALUE));
assertEquals("tesX", StringUtils.mask("test", 'X', 1, Integer.MAX_VALUE, Integer.MAX_VALUE - 5));
assertEquals("tXst", StringUtils.mask("test", 'X', 1, Integer.MAX_VALUE -1, Integer.MAX_VALUE));
assertEquals("teXt", StringUtils.mask("test", 'X', 1, Integer.MAX_VALUE, Integer.MAX_VALUE -1));
assertEquals("tXXst", StringUtils.mask("teest", 'X', 2, Integer.MAX_VALUE -1, Integer.MAX_VALUE));
assertEquals("teXXt", StringUtils.mask("teest", 'X', 2, Integer.MAX_VALUE, Integer.MAX_VALUE -1));
}
}