Refactor the input buffer filter to use a context as the output buffer

filter does. Ensure that the filter properly handles the non blocking
case, both when a downstream filter returns EAGAIN, or if a filter
returns APR_SUCCESS and an empty brigade.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@718082 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/modules/filters/mod_buffer.c b/modules/filters/mod_buffer.c
index f7231dad4d055cb820cdeec216380d6036d5afa1..c8e3bf38e21b6f620fd3c174d3284b8879a057bb 100644 (file)
--- a/modules/filters/mod_buffer.c
+++ b/modules/filters/mod_buffer.c
@@ -43,7 +43,10 @@ typedef struct buffer_conf {
 
 typedef struct buffer_ctx {
     apr_bucket_brigade *bb;
+    apr_bucket_brigade *tmp;
     buffer_conf *conf;
+    apr_off_t remaining;
+    int seen_eos;
 } buffer_ctx;
 
 /**
@@ -158,11 +161,9 @@ static apr_status_t buffer_out_filter(ap_filter_t *f, apr_bucket_brigade *bb) {
  */
 static apr_status_t buffer_in_filter(ap_filter_t *f, apr_bucket_brigade *bb,
         ap_input_mode_t mode, apr_read_type_e block, apr_off_t readbytes) {
-    apr_bucket *e;
-    apr_bucket_brigade *tmp;
+    apr_bucket *e, *after;
     apr_status_t rv;
-    buffer_conf *c;
-    apr_off_t remaining;
+    buffer_ctx *ctx = f->ctx;
 
     /* buffer on main requests only */
     if (!ap_is_initial_req(f->r)) {
@@ -170,65 +171,84 @@ static apr_status_t buffer_in_filter(ap_filter_t *f, apr_bucket_brigade *bb,
         return ap_get_brigade(f->next, bb, mode, block, readbytes);
     }
 
+    /* first time in? create a context */
+    if (!ctx) {
+        ctx = f->ctx = apr_pcalloc(f->r->pool, sizeof(*ctx));
+        ctx->bb = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
+        ctx->tmp = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
+        ctx->conf = ap_get_module_config(f->r->per_dir_config, &buffer_module);
+    }
+
     /* just get out of the way of things we don't want. */
     if (mode != AP_MODE_READBYTES) {
         return ap_get_brigade(f->next, bb, mode, block, readbytes);
     }
 
-    c = ap_get_module_config(f->r->per_dir_config, &buffer_module);
-
-    tmp = apr_brigade_create(f->r->pool, f->c->bucket_alloc);
-
-    remaining = readbytes;
-    while (remaining > 0) {
-        const char *data;
-        apr_off_t len;
-        apr_size_t size;
+    /* if our buffer is empty, read off the network until the buffer is full */
+    if (APR_BRIGADE_EMPTY(ctx->bb)) {
+        ctx->remaining = ctx->conf->size;
 
-        rv = ap_get_brigade(f->next, tmp, mode, block, remaining);
+        while (!ctx->seen_eos && ctx->remaining > 0) {
+            const char *data;
+            apr_size_t size = 0;
 
-        /* if an error was received, bail out now */
-        if (rv != APR_SUCCESS) {
-            APR_BRIGADE_CONCAT(bb, tmp);
-            return rv;
-        }
+            rv = ap_get_brigade(f->next, ctx->tmp, mode, block, ctx->remaining);
 
-        apr_brigade_length(tmp, 1, &len);
-        remaining -= len;
-
-        for (e = APR_BRIGADE_FIRST(tmp); e != APR_BRIGADE_SENTINEL(tmp); e
-                = APR_BUCKET_NEXT(e)) {
-
-            /* if we see an EOS, we are done */
-            if (APR_BUCKET_IS_EOS(e)) {
-                APR_BUCKET_REMOVE(e);
-                APR_BRIGADE_INSERT_TAIL(bb, e);
-                remaining = 0;
-                break;
-            }
-
-            /* pass flush buckets through */
-            if (APR_BUCKET_IS_FLUSH(e)) {
-                APR_BUCKET_REMOVE(e);
-                APR_BRIGADE_INSERT_TAIL(bb, e);
-                continue;
+            /* if an error was received, bail out now. If the error is
+             * EAGAIN and we have not yet seen an EOS, we will definitely
+             * be called again, at which point we will send our buffered
+             * data. Instead of sending EAGAIN, some filters return an
+             * empty brigade instead when data is not yet available. In
+             * this case, pass through the APR_SUCCESS and emulate the
+             * underlying filter.
+             */
+            if (rv != APR_SUCCESS || APR_BRIGADE_EMPTY(ctx->tmp)) {
+                return rv;
             }
 
-            /* pass metadata buckets through */
-            if (APR_BUCKET_IS_METADATA(e)) {
-                APR_BUCKET_REMOVE(e);
-                APR_BRIGADE_INSERT_TAIL(bb, e);
-                continue;
-            }
+            for (e = APR_BRIGADE_FIRST(ctx->tmp); e != APR_BRIGADE_SENTINEL(
+                    ctx->tmp); e = APR_BUCKET_NEXT(e)) {
+
+                /* if we see an EOS, we are done */
+                if (APR_BUCKET_IS_EOS(e)) {
+                    APR_BUCKET_REMOVE(e);
+                    APR_BRIGADE_INSERT_TAIL(ctx->bb, e);
+                    ctx->seen_eos = 1;
+                    break;
+                }
+
+                /* pass flush and metadata buckets through */
+                if (APR_BUCKET_IS_FLUSH(e) || APR_BUCKET_IS_METADATA(e)) {
+                    APR_BUCKET_REMOVE(e);
+                    APR_BRIGADE_INSERT_TAIL(bb, e);
+                    continue;
+                }
+
+                /* read the bucket in, pack it into the buffer */
+                if (APR_SUCCESS == (rv = apr_bucket_read(e, &data, &size,
+                        APR_BLOCK_READ))) {
+                    apr_brigade_write(ctx->bb, NULL, NULL, data, size);
+                    ctx->remaining -= size;
+                    apr_bucket_delete(e);
+                } else {
+                    return rv;
+                }
 
-            /* read */
-            if (APR_SUCCESS == (rv = apr_bucket_read(e, &data, &size,
-                    APR_BLOCK_READ))) {
-                apr_brigade_write(bb, NULL, NULL, data, size);
             }
+        }
+    }
 
+    /* give the caller the data they asked for from the buffer */
+    apr_brigade_partition(ctx->bb, readbytes, &after);
+    e = APR_BRIGADE_FIRST(ctx->bb);
+    while (e != after) {
+        if (APR_BUCKET_IS_EOS(e)) {
+            /* last bucket read, step out of the way */
+            ap_remove_input_filter(f);
         }
-        apr_brigade_cleanup(tmp);
+        APR_BUCKET_REMOVE(e);
+        APR_BRIGADE_INSERT_TAIL(bb, e);
+        e = APR_BRIGADE_FIRST(ctx->bb);
     }
 
     return APR_SUCCESS;