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Micro-optimize copy instructions in DeltaEncoder 

The copy instruction formatter should not to compute the shifts and
masks twice.  Instead compute them once and assume there is a register
available to store the temporary "b" for compare with 0.

Change-Id: Ic7826f29dca67b16903d8f790bdf785eb478c10d
This commit is contained in:
Shawn Pearce 2013-04-11 01:11:11 -07:00
parent 1db50c9d91
commit 0f32901ab7
1 changed files with 19 additions and 18 deletions
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37
org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/pack/DeltaEncoder.java
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@ -134,7 +134,7 @@ private void writeVarint(long sz) throws IOException {
}
buf[p++] = (byte) (((int) sz) & 0x7f);
size += p;
if (limit <= 0 || size < limit)
if (limit == 0 || size < limit)
out.write(buf, 0, p);
}
@ -189,7 +189,7 @@ public boolean insert(byte[] text, int off, int cnt)
throws IOException {
if (cnt <= 0)
return true;
if (0 < limit) {
if (limit != 0) {
int hdrs = cnt / MAX_INSERT_DATA_SIZE;
if (cnt % MAX_INSERT_DATA_SIZE != 0)
hdrs++;
@ -236,7 +236,7 @@ public boolean copy(long offset, int cnt) throws IOException {
cnt -= MAX_V2_COPY;
if (buf.length < p + MAX_COPY_CMD_SIZE) {
if (0 < limit && limit < size + p)
if (limit != 0 && limit < size + p)
return false;
out.write(buf, 0, p);
size += p;
@ -245,7 +245,7 @@ public boolean copy(long offset, int cnt) throws IOException {
}
p = encodeCopy(p, offset, cnt);
if (0 < limit && limit < size + p)
if (limit != 0 && limit < size + p)
return false;
out.write(buf, 0, p);
size += p;
@ -255,36 +255,37 @@ public boolean copy(long offset, int cnt) throws IOException {
private int encodeCopy(int p, long offset, int cnt) {
int cmd = 0x80;
final int cmdPtr = p++; // save room for the command
byte b;
if ((offset & 0xff) != 0) {
if ((b = (byte) (offset & 0xff)) != 0) {
cmd |= 0x01;
buf[p++] = (byte) (offset & 0xff);
buf[p++] = b;
}
if ((offset & (0xff << 8)) != 0) {
if ((b = (byte) ((offset >>> 8) & 0xff)) != 0) {
cmd |= 0x02;
buf[p++] = (byte) ((offset >>> 8) & 0xff);
buf[p++] = b;
}
if ((offset & (0xff << 16)) != 0) {
if ((b = (byte) ((offset >>> 16) & 0xff)) != 0) {
cmd |= 0x04;
buf[p++] = (byte) ((offset >>> 16) & 0xff);
buf[p++] = b;
}
if ((offset & (0xff << 24)) != 0) {
if ((b = (byte) ((offset >>> 24) & 0xff)) != 0) {
cmd |= 0x08;
buf[p++] = (byte) ((offset >>> 24) & 0xff);
buf[p++] = b;
}
if (cnt != MAX_V2_COPY) {
if ((cnt & 0xff) != 0) {
if ((b = (byte) (cnt & 0xff)) != 0) {
cmd |= 0x10;
buf[p++] = (byte) (cnt & 0xff);
buf[p++] = b;
}
if ((cnt & (0xff << 8)) != 0) {
if ((b = (byte) ((cnt >>> 8) & 0xff)) != 0) {
cmd |= 0x20;
buf[p++] = (byte) ((cnt >>> 8) & 0xff);
buf[p++] = b;
}
if ((cnt & (0xff << 16)) != 0) {
if ((b = (byte) ((cnt >>> 16) & 0xff)) != 0) {
cmd |= 0x40;
buf[p++] = (byte) ((cnt >>> 16) & 0xff);
buf[p++] = b;
}
}