On Sunday 18 April 2010 16:13:01 Andreas Gruenbacher wrote:
> Hello,
>
> here is a change to diffseq whcih I need in GNU patch: patch has a historic
> feature called "plan B" for when only little memory is available; it then
> doesn't load the entire patch and file to be patched into memory. To
> support this, the file and patch are accessed through functions rather
> than directly as arrays. (This feature is probably relatively worthless
> these days except for weird corner cases, but I would still like to keep
> it exactly for such corner cases.)
>
> Is this change acceptable?
The patch was getting word wrapped, sorry -- here is the correct version.
Andreas
* diffseq (EQUAL_IDX): When this macro is defined instead of EQUAL, do
not assume that the x and y vectors are directly accessible as xvec and
yvec. Use EQUAL_IDX() instead of EQUAL() to compare vector elements.
Signed-off-by: Andreas Gruenbacher <agr...@suse.de>
---
lib/diffseq.h | 28 ++++++++++++++++++++--------
1 files changed, 20 insertions(+), 8 deletions(-)
diff --git a/lib/diffseq.h b/lib/diffseq.h
index d9c871b..02df835 100644
--- a/lib/diffseq.h
+++ b/lib/diffseq.h
@@ -41,8 +41,9 @@
/* Before including this file, you need to define:
ELEMENT The element type of the vectors being compared.
- EQUAL A two-argument macro that tests two elements for
- equality.
+ EQUAL(x, y) or EQUAL_IDX(ctxt, xoff, yoff)
+ Test two ELEMENTs for equality, or test the
+ elements at offsets xoff and yoff for equality.
OFFSET A signed integer type sufficient to hold the
difference between two indices. Usually
something like ssize_t.
@@ -87,14 +88,20 @@
# endif
#endif
+#ifdef EQUAL
+# define EQUAL_IDX(ctxt, xoff, yoff) EQUAL(xv[xoff], yv[yoff])
+#endif
+
/*
* Context of comparison operation.
*/
struct context
{
+#ifdef EQUAL
/* Vectors being compared. */
ELEMENT const *xvec;
ELEMENT const *yvec;
+#endif
/* Extra fields. */
EXTRA_CONTEXT_FIELDS
@@ -170,8 +177,10 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
bool find_minimal,
{
OFFSET *const fd = ctxt->fdiag; /* Give the compiler a chance. */
OFFSET *const bd = ctxt->bdiag; /* Additional help for the compiler. */
+#ifdef EQUAL
ELEMENT const *const xv = ctxt->xvec; /* Still more help for the compiler. */
ELEMENT const *const yv = ctxt->yvec; /* And more and more . . . */
+#endif
const OFFSET dmin = xoff - ylim; /* Minimum valid diagonal. */
const OFFSET dmax = xlim - yoff; /* Maximum valid diagonal. */
const OFFSET fmid = xoff - yoff; /* Center diagonal of top-down search.
*/
@@ -210,7 +219,7 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
bool find_minimal,
OFFSET x0 = tlo < thi ? thi : tlo + 1;
for (x = x0, y = x0 - d;
- x < xlim && y < ylim && EQUAL (xv[x], yv[y]);
+ x < xlim && y < ylim && EQUAL_IDX (ctxt, x, y);
x++, y++)
continue;
if (x - x0 > SNAKE_LIMIT)
@@ -243,7 +252,7 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
bool find_minimal,
OFFSET x0 = tlo < thi ? tlo : thi - 1;
for (x = x0, y = x0 - d;
- xoff < x && yoff < y && EQUAL (xv[x - 1], yv[y - 1]);
+ xoff < x && yoff < y && EQUAL_IDX (ctxt, x - 1, y - 1);
x--, y--)
continue;
if (x0 - x > SNAKE_LIMIT)
@@ -292,7 +301,7 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
bool find_minimal,
that it end with a significant snake. */
int k;
- for (k = 1; EQUAL (xv[x - k], yv[y - k]); k++)
+ for (k = 1; EQUAL_IDX (ctxt, x - k, y - k); k++)
if (k == SNAKE_LIMIT)
{
best = v;
@@ -331,7 +340,7 @@ diag (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
bool find_minimal,
that it end with a significant snake. */
int k;
- for (k = 0; EQUAL (xv[x + k], yv[y + k]); k++)
+ for (k = 0; EQUAL_IDX (ctxt, x + k, y + k); k++)
if (k == SNAKE_LIMIT - 1)
{
best = v;
@@ -438,18 +447,20 @@ static bool
compareseq (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET ylim,
bool find_minimal, struct context *ctxt)
{
+#ifdef EQUAL
ELEMENT const *xv = ctxt->xvec; /* Help the compiler. */
ELEMENT const *yv = ctxt->yvec;
+#endif
/* Slide down the bottom initial diagonal. */
- while (xoff < xlim && yoff < ylim && EQUAL (xv[xoff], yv[yoff]))
+ while (xoff < xlim && yoff < ylim && EQUAL_IDX (ctxt, xoff, yoff))
{
xoff++;
yoff++;
}
/* Slide up the top initial diagonal. */
- while (xoff < xlim && yoff < ylim && EQUAL (xv[xlim - 1], yv[ylim - 1]))
+ while (xoff < xlim && yoff < ylim && EQUAL_IDX (ctxt, xlim - 1, ylim - 1))
{
xlim--;
ylim--;
@@ -491,6 +502,7 @@ compareseq (OFFSET xoff, OFFSET xlim, OFFSET yoff, OFFSET
ylim,
#undef ELEMENT
#undef EQUAL
+#undef EQUAL_IDX
#undef OFFSET
#undef EXTRA_CONTEXT_FIELDS
#undef NOTE_DELETE
--
1.7.1.rc1.12.ga601
