From fbd87029cfc494a72bb73ade27ef46382c5bc832 Mon Sep 17 00:00:00 2001 From: Pádraig Brady Date: Thu, 20 Nov 2008 22:49:02 +0000 Subject: dd: avoid unnecessary memory copies * src/dd.c (scanargs): When not otherwise required (e.g. for conversion), use two-buffer mode only when the input and output buffer sizes differ. Before, some of the most basic invocations of dd, e.g., dd < in > out, would unnecessarily use separate buffers and perform memory copies between them. --- src/dd.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/src/dd.c b/src/dd.c index f598e44cd..e1e38e954 100644 --- a/src/dd.c +++ b/src/dd.c @@ -998,13 +998,11 @@ scanargs (int argc, char *const *argv) { invalid |= ! (0 < n && n <= MAX_BLOCKSIZE (INPUT_BLOCK_SLOP)); input_blocksize = n; - conversions_mask |= C_TWOBUFS; } else if (operand_is (name, "obs")) { invalid |= ! (0 < n && n <= MAX_BLOCKSIZE (OUTPUT_BLOCK_SLOP)); output_blocksize = n; - conversions_mask |= C_TWOBUFS; } else if (operand_is (name, "bs")) { @@ -1036,15 +1034,12 @@ scanargs (int argc, char *const *argv) if (blocksize) input_blocksize = output_blocksize = blocksize; - /* If bs= was given, both `input_blocksize' and `output_blocksize' will - have been set to positive values. If either has not been set, - bs= was not given, so make sure two buffers are used. */ - if (input_blocksize == 0 || output_blocksize == 0) - conversions_mask |= C_TWOBUFS; if (input_blocksize == 0) input_blocksize = DEFAULT_BLOCKSIZE; if (output_blocksize == 0) output_blocksize = DEFAULT_BLOCKSIZE; + if (input_blocksize != output_blocksize) + conversions_mask |= C_TWOBUFS; if (conversion_blocksize == 0) conversions_mask &= ~(C_BLOCK | C_UNBLOCK); -- cgit v1.2.3-70-g09d2