diff options
Diffstat (limited to 'java/util/zip/Adler32.java')
| -rw-r--r-- | java/util/zip/Adler32.java | 66 |
1 files changed, 33 insertions, 33 deletions
diff --git a/java/util/zip/Adler32.java b/java/util/zip/Adler32.java index 7c4113840..cc27da927 100644 --- a/java/util/zip/Adler32.java +++ b/java/util/zip/Adler32.java @@ -45,8 +45,8 @@ package java.util.zip; */ /** - * Computes Adler32 checksum for a stream of data. An Adler32 - * checksum is not as reliable as a CRC32 checksum, but a lot faster to + * Computes Adler32 checksum for a stream of data. An Adler32 + * checksum is not as reliable as a CRC32 checksum, but a lot faster to * compute. *<p> * The specification for Adler32 may be found in RFC 1950. @@ -60,7 +60,7 @@ package java.util.zip; * (excluding any dictionary data) computed according to Adler-32 * algorithm. This algorithm is a 32-bit extension and improvement * of the Fletcher algorithm, used in the ITU-T X.224 / ISO 8073 - * standard. + * standard. *<p> * Adler-32 is composed of two sums accumulated per byte: s1 is * the sum of all bytes, s2 is the sum of all s1 values. Both sums @@ -103,13 +103,13 @@ public class Adler32 implements Checksum private int checksum; //we do all in int. //Note that java doesn't have unsigned integers, - //so we have to be careful with what arithmetic - //we do. We return the checksum as a long to + //so we have to be careful with what arithmetic + //we do. We return the checksum as a long to //avoid sign confusion. /** - * Creates a new instance of the <code>Adler32</code> class. - * The checksum starts off with a value of 1. + * Creates a new instance of the <code>Adler32</code> class. + * The checksum starts off with a value of 1. */ public Adler32 () { @@ -119,13 +119,13 @@ public class Adler32 implements Checksum /** * Resets the Adler32 checksum to the initial value. */ - public void reset () + public void reset () { - checksum = 1; //Initialize to 1 + checksum = 1; //Initialize to 1 } /** - * Updates the checksum with the byte b. + * Updates the checksum with the byte b. * * @param bval the data value to add. The high byte of the int is ignored. */ @@ -135,16 +135,16 @@ public class Adler32 implements Checksum //would rather not have that overhead int s1 = checksum & 0xffff; int s2 = checksum >>> 16; - + s1 = (s1 + (bval & 0xFF)) % BASE; s2 = (s1 + s2) % BASE; - + checksum = (s2 << 16) + s1; } /** - * Updates the checksum with the bytes taken from the array. - * + * Updates the checksum with the bytes taken from the array. + * * @param buffer an array of bytes */ public void update (byte[] buffer) @@ -153,8 +153,8 @@ public class Adler32 implements Checksum } /** - * Updates the checksum with the bytes taken from the array. - * + * Updates the checksum with the bytes taken from the array. + * * @param buf an array of bytes * @param off the start of the data used for this update * @param len the number of bytes to use for this update @@ -167,31 +167,31 @@ public class Adler32 implements Checksum while (len > 0) { - // We can defer the modulo operation: - // s1 maximally grows from 65521 to 65521 + 255 * 3800 - // s2 maximally grows by 3800 * median(s1) = 2090079800 < 2^31 - int n = 3800; - if (n > len) - n = len; - len -= n; - while (--n >= 0) - { - s1 = s1 + (buf[off++] & 0xFF); - s2 = s2 + s1; - } - s1 %= BASE; - s2 %= BASE; + // We can defer the modulo operation: + // s1 maximally grows from 65521 to 65521 + 255 * 3800 + // s2 maximally grows by 3800 * median(s1) = 2090079800 < 2^31 + int n = 3800; + if (n > len) + n = len; + len -= n; + while (--n >= 0) + { + s1 = s1 + (buf[off++] & 0xFF); + s2 = s2 + s1; + } + s1 %= BASE; + s2 %= BASE; } /*Old implementation, borrowed from somewhere: int n; - + while (len-- > 0) { - s1 = (s1 + (bs[offset++] & 0xff)) % BASE; + s1 = (s1 + (bs[offset++] & 0xff)) % BASE; s2 = (s2 + s1) % BASE; }*/ - + checksum = (s2 << 16) | s1; } |