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Use TRANSIENT buckets in mod_deflate output filters to save a little RAM/CPU #622

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Use TRANSIENT buckets in mod_deflate output filters to save a little RAM/CPU #622

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35 changes: 25 additions & 10 deletions modules/filters/mod_deflate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -412,13 +412,18 @@ typedef struct deflate_ctx_t

/* Number of validation bytes (CRC and length) after the compressed data */
#define VALIDATION_SIZE 8

/* Do not update ctx->crc, see comment in flush_libz_buffer */
#define NO_UPDATE_CRC 0
#define NO_UPDATE_CRC 0x0
/* Do update ctx->crc, see comment in flush_libz_buffer */
#define UPDATE_CRC 1
#define UPDATE_CRC 0x1
/* Use a transient bucket, which is ONLY safe if the bucket will be
* passed down the filter chain immediately before the zlib stream is
* used again. */
#define TRANSIENT 0x2

static void consume_buffer(deflate_ctx *ctx, deflate_filter_config *c,
int len, int crc, apr_bucket_brigade *bb)
int len, unsigned int flags, apr_bucket_brigade *bb)
{
apr_bucket *b;

Expand All @@ -427,12 +432,16 @@ static void consume_buffer(deflate_ctx *ctx, deflate_filter_config *c,
* inflate action where we need to do a crc on the output, whereas
* in the deflate case we need to do a crc on the input
*/
if (crc) {
if (flags & UPDATE_CRC) {
ctx->crc = crc32(ctx->crc, (const Bytef *)ctx->buffer, len);
}

b = apr_bucket_heap_create((char *)ctx->buffer, len, NULL,
bb->bucket_alloc);
if (flags & TRANSIENT)
b = apr_bucket_transient_create((char *)ctx->buffer, len,
bb->bucket_alloc);
else
b = apr_bucket_heap_create((char *)ctx->buffer, len, NULL,
bb->bucket_alloc);
APR_BRIGADE_INSERT_TAIL(bb, b);

ctx->stream.next_out = ctx->buffer;
Expand All @@ -441,7 +450,7 @@ static void consume_buffer(deflate_ctx *ctx, deflate_filter_config *c,

static int flush_libz_buffer(deflate_ctx *ctx, deflate_filter_config *c,
int (*libz_func)(z_streamp, int), int flush,
int crc)
unsigned int flags)
{
int zRC = Z_OK;
int done = 0;
Expand All @@ -450,7 +459,7 @@ static int flush_libz_buffer(deflate_ctx *ctx, deflate_filter_config *c,
for (;;) {
deflate_len = c->bufferSize - ctx->stream.avail_out;
if (deflate_len > 0) {
consume_buffer(ctx, c, deflate_len, crc, ctx->bb);
consume_buffer(ctx, c, deflate_len, flags, ctx->bb);
}

if (done)
Expand Down Expand Up @@ -1019,7 +1028,10 @@ static apr_status_t deflate_out_filter(ap_filter_t *f,

while (ctx->stream.avail_in != 0) {
if (ctx->stream.avail_out == 0) {
consume_buffer(ctx, c, c->bufferSize, NO_UPDATE_CRC, ctx->bb);
/* Use a transient bucket since it will be sent down
* the filter chain immediately. */
consume_buffer(ctx, c, c->bufferSize,
NO_UPDATE_CRC|TRANSIENT, ctx->bb);

/* Send what we have right now to the next filter. */
rv = ap_pass_brigade(f->next, ctx->bb);
Expand Down Expand Up @@ -1840,7 +1852,10 @@ static apr_status_t inflate_out_filter(ap_filter_t *f,

while (ctx->stream.avail_in != 0) {
if (ctx->stream.avail_out == 0) {
consume_buffer(ctx, c, c->bufferSize, UPDATE_CRC, ctx->bb);
/* Use a transient bucket since it will be sent down
* the filter chain immediately. */
consume_buffer(ctx, c, c->bufferSize,
UPDATE_CRC|TRANSIENT, ctx->bb);

/* Send what we have right now to the next filter. */
rv = ap_pass_brigade(f->next, ctx->bb);
Expand Down
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