# HG changeset patch
# User Roman Arutyunyan <arut@nginx.com>
# Date 1640359043 -10800
# Node ID 6ccf3867959aa1c377261604b631f70bf1013ea1
# Parent  56dec0d4e5b1ac034e5d1aeb98cad9e238ccdf58
QUIC: refactored ngx_quic_order_bufs() and ngx_quic_split_bufs().

They are replaced with ngx_quic_write_chain() and ngx_quic_read_chain().
These functions represent the API to data buffering.

The first function adds data of given size at given offset to the buffer.
Now it returns the unwritten part of the chain similar to c->send_chain().

The second function returns data of given size from the beginning of the buffer.
Its second argument and return value are swapped compared to
ngx_quic_split_bufs() to better match ngx_quic_write_chain().

Added, returned and stored data are regular ngx_chain_t/ngx_buf_t chains.
Missing data is marked with b->sync flag.

The functions are now used in both send and recv data chains in QUIC streams.

diff --git a/src/event/quic/ngx_event_quic_frames.c b/src/event/quic/ngx_event_quic_frames.c
--- a/src/event/quic/ngx_event_quic_frames.c
+++ b/src/event/quic/ngx_event_quic_frames.c
@@ -13,10 +13,6 @@
 #define NGX_QUIC_BUFFER_SIZE  4096
 
 
-static ngx_chain_t *ngx_quic_split_bufs(ngx_connection_t *c, ngx_chain_t *in,
-    size_t len);
-
-
 ngx_quic_frame_t *
 ngx_quic_alloc_frame(ngx_connection_t *c)
 {
@@ -243,8 +239,8 @@ ngx_quic_split_frame(ngx_connection_t *c
     onf->length = shrink;
     nf->len = ngx_quic_create_frame(NULL, nf);
 
-    nf->data = ngx_quic_split_bufs(c, f->data, of->length);
-    if (nf->data == NGX_CHAIN_ERROR) {
+    f->data = ngx_quic_read_chain(c, &nf->data, of->length);
+    if (f->data == NGX_CHAIN_ERROR) {
         return NGX_ERROR;
     }
 
@@ -254,36 +250,47 @@ ngx_quic_split_frame(ngx_connection_t *c
 }
 
 
-static ngx_chain_t *
-ngx_quic_split_bufs(ngx_connection_t *c, ngx_chain_t *in, size_t len)
+ngx_chain_t *
+ngx_quic_read_chain(ngx_connection_t *c, ngx_chain_t **chain, off_t limit)
 {
-    size_t                  n;
+    off_t                   n;
     ngx_buf_t              *b;
-    ngx_chain_t            *out;
+    ngx_chain_t            *out, *in, *cl, **ll;
     ngx_quic_connection_t  *qc;
 
     qc = ngx_quic_get_connection(c);
 
-    while (in) {
-        n = ngx_buf_size(in->buf);
+    out = *chain;
 
-        if (n == len) {
-            out = in->next;
-            in->next = NULL;
-            return out;
+    for (ll = &out; *ll; ll = &(*ll)->next) {
+        b = (*ll)->buf;
+
+        if (b->sync) {
+            /* hole */
+            break;
         }
 
-        if (n > len) {
+        if (limit == 0) {
             break;
         }
 
-        len -= n;
-        in = in->next;
+        n = b->last - b->pos;
+
+        if (n > limit) {
+            goto split;
+        }
+
+        limit -= n;
     }
 
-    if (in == NULL) {
-        return NULL;
-    }
+    *chain = *ll;
+    *ll = NULL;
+
+    return out;
+
+split:
+
+    in = *ll;
 
     /* split in->buf by creating shadow bufs which reference it */
 
@@ -305,8 +312,8 @@ ngx_quic_split_bufs(ngx_connection_t *c,
         in->buf = b;
     }
 
-    out = ngx_alloc_chain_link(c->pool);
-    if (out == NULL) {
+    cl = ngx_alloc_chain_link(c->pool);
+    if (cl == NULL) {
         return NGX_CHAIN_ERROR;
     }
 
@@ -317,21 +324,23 @@ ngx_quic_split_bufs(ngx_connection_t *c,
     } else {
         b = ngx_alloc_buf(c->pool);
         if (b == NULL) {
-            ngx_free_chain(c->pool, out);
+            ngx_free_chain(c->pool, cl);
             return NGX_CHAIN_ERROR;
         }
     }
 
-    out->buf = b;
-    out->next = in->next;
+    cl->buf = b;
+    cl->next = in->next;
     in->next = NULL;
+    *chain = cl;
 
     *b = *in->buf;
     b->last_shadow = 0;
-    b->pos = b->pos + len;
+    b->pos += limit;
 
     in->buf->shadow = b;
-    in->buf->last = in->buf->pos + len;
+    in->buf->last = b->pos;
+    in->buf->last_buf = 0;
 
     return out;
 }
@@ -480,8 +489,8 @@ done:
 }
 
 
-ngx_int_t
-ngx_quic_order_bufs(ngx_connection_t *c, ngx_chain_t **out, ngx_chain_t *in,
+ngx_chain_t *
+ngx_quic_write_chain(ngx_connection_t *c, ngx_chain_t **chain, ngx_chain_t *in,
     off_t limit, off_t offset)
 {
     off_t         n;
@@ -490,18 +499,18 @@ ngx_quic_order_bufs(ngx_connection_t *c,
     ngx_chain_t  *cl, *sl;
 
     while (in && limit) {
-        cl = *out;
+        cl = *chain;
 
         if (cl == NULL) {
             cl = ngx_quic_alloc_buf(c);
             if (cl == NULL) {
-                return NGX_ERROR;
+                return NGX_CHAIN_ERROR;
             }
 
             cl->buf->last = cl->buf->end;
             cl->buf->sync = 1; /* hole */
             cl->next = NULL;
-            *out = cl;
+            *chain = cl;
         }
 
         b = cl->buf;
@@ -509,17 +518,25 @@ ngx_quic_order_bufs(ngx_connection_t *c,
 
         if (n <= offset) {
             offset -= n;
-            out = &cl->next;
+            chain = &cl->next;
             continue;
         }
 
         if (b->sync && offset > 0) {
-            sl = ngx_quic_split_bufs(c, cl, offset);
-            if (sl == NGX_CHAIN_ERROR) {
-                return NGX_ERROR;
+            /* split hole at offset */
+
+            b->sync = 0;
+
+            sl = ngx_quic_read_chain(c, &cl, offset);
+            if (cl == NGX_CHAIN_ERROR) {
+                return NGX_CHAIN_ERROR;
             }
 
-            cl->next = sl;
+            sl->buf->sync = 1;
+            cl->buf->sync = 1;
+
+            *chain = sl;
+            sl->next = cl;
             continue;
         }
 
@@ -541,18 +558,29 @@ ngx_quic_order_bufs(ngx_connection_t *c,
             }
         }
 
+        if (b->sync && p == b->last) {
+            b->sync = 0;
+            continue;
+        }
+
         if (b->sync && p != b->pos) {
-            sl = ngx_quic_split_bufs(c, cl, p - b->pos);
+            /* split hole at p - b->pos */
+
+            b->sync = 0;
+
+            sl = ngx_quic_read_chain(c, &cl, p - b->pos);
             if (sl == NGX_CHAIN_ERROR) {
-                return NGX_ERROR;
+                return NGX_CHAIN_ERROR;
             }
 
-            cl->next = sl;
-            cl->buf->sync = 0;
+            cl->buf->sync = 1;
+
+            *chain = sl;
+            sl->next = cl;
         }
     }
 
-    return NGX_OK;
+    return in;
 }
 
 
diff --git a/src/event/quic/ngx_event_quic_frames.h b/src/event/quic/ngx_event_quic_frames.h
--- a/src/event/quic/ngx_event_quic_frames.h
+++ b/src/event/quic/ngx_event_quic_frames.h
@@ -30,7 +30,9 @@ ngx_chain_t *ngx_quic_copy_chain(ngx_con
     size_t limit);
 void ngx_quic_trim_bufs(ngx_chain_t *in, size_t size);
 void ngx_quic_free_bufs(ngx_connection_t *c, ngx_chain_t *in);
-ngx_int_t ngx_quic_order_bufs(ngx_connection_t *c, ngx_chain_t **out,
+ngx_chain_t *ngx_quic_read_chain(ngx_connection_t *c, ngx_chain_t **chain,
+    off_t limit);
+ngx_chain_t *ngx_quic_write_chain(ngx_connection_t *c, ngx_chain_t **chain,
     ngx_chain_t *in, off_t limit, off_t offset);
 
 #if (NGX_DEBUG)
diff --git a/src/event/quic/ngx_event_quic_ssl.c b/src/event/quic/ngx_event_quic_ssl.c
--- a/src/event/quic/ngx_event_quic_ssl.c
+++ b/src/event/quic/ngx_event_quic_ssl.c
@@ -369,8 +369,14 @@ ngx_quic_handle_crypto_frame(ngx_connect
     }
 
     if (f->offset > ctx->crypto_received) {
-        return ngx_quic_order_bufs(c, &ctx->crypto, frame->data, f->length,
-                                   f->offset - ctx->crypto_received);
+        if (ngx_quic_write_chain(c, &ctx->crypto, frame->data, f->length,
+                                 f->offset - ctx->crypto_received)
+            == NGX_CHAIN_ERROR)
+        {
+            return NGX_ERROR;
+        }
+
+        return NGX_OK;
     }
 
     ngx_quic_trim_bufs(frame->data, ctx->crypto_received - f->offset);
diff --git a/src/event/quic/ngx_event_quic_streams.c b/src/event/quic/ngx_event_quic_streams.c
--- a/src/event/quic/ngx_event_quic_streams.c
+++ b/src/event/quic/ngx_event_quic_streams.c
@@ -732,9 +732,9 @@ ngx_quic_empty_handler(ngx_event_t *ev)
 static ssize_t
 ngx_quic_stream_recv(ngx_connection_t *c, u_char *buf, size_t size)
 {
-    ssize_t             len, n;
+    ssize_t             len;
     ngx_buf_t          *b;
-    ngx_chain_t        *cl, **ll;
+    ngx_chain_t        *cl, *in;
     ngx_event_t        *rev;
     ngx_connection_t   *pc;
     ngx_quic_stream_t  *qs;
@@ -764,33 +764,20 @@ ngx_quic_stream_recv(ngx_connection_t *c
         return NGX_AGAIN;
     }
 
-    len = 0;
-    cl = qs->in;
-
-    for (ll = &cl; *ll; ll = &(*ll)->next) {
-        b = (*ll)->buf;
-
-        if (b->sync) {
-            /* hole */
-            break;
-        }
-
-        n = ngx_min(b->last - b->pos, (ssize_t) size);
-        buf = ngx_cpymem(buf, b->pos, n);
-
-        len += n;
-        size -= n;
-        b->pos += n;
-
-        if (b->pos != b->last) {
-            break;
-        }
+    in = ngx_quic_read_chain(pc, &qs->in, size);
+    if (in == NGX_CHAIN_ERROR) {
+        return NGX_ERROR;
     }
 
-    qs->in = *ll;
-    *ll = NULL;
+    len = 0;
 
-    ngx_quic_free_bufs(pc, cl);
+    for (cl = in; cl; cl = cl->next) {
+        b = cl->buf;
+        len += b->last - b->pos;
+        buf = ngx_cpymem(buf, b->pos, b->last - b->pos);
+    }
+
+    ngx_quic_free_bufs(pc, in);
 
     if (qs->in == NULL) {
         rev->ready = rev->pending_eof;
@@ -837,10 +824,9 @@ ngx_quic_stream_send(ngx_connection_t *c
 static ngx_chain_t *
 ngx_quic_stream_send_chain(ngx_connection_t *c, ngx_chain_t *in, off_t limit)
 {
-    size_t                  n, flow;
-    ngx_buf_t              *b;
+    off_t                   n, flow;
     ngx_event_t            *wev;
-    ngx_chain_t            *out, **ll;
+    ngx_chain_t            *out, *cl;
     ngx_connection_t       *pc;
     ngx_quic_frame_t       *frame;
     ngx_quic_stream_t      *qs;
@@ -861,38 +847,35 @@ ngx_quic_stream_send_chain(ngx_connectio
         return in;
     }
 
-    n = (limit && (size_t) limit < flow) ? (size_t) limit : flow;
-
-    if (ngx_quic_order_bufs(pc, &qs->out, in, n, 0) != NGX_OK) {
-        return NGX_CHAIN_ERROR;
+    if (limit == 0 || limit > flow) {
+        limit = flow;
     }
 
     n = 0;
-    out = qs->out;
 
-    for (ll = &out; *ll; ll = &(*ll)->next) {
-        b = (*ll)->buf;
-
-        if (b->sync) {
-            /* hole */
+    for (cl = in; cl; cl = cl->next) {
+        n += cl->buf->last - cl->buf->pos;
+        if (n >= limit) {
+            n = limit;
             break;
         }
-
-        n += b->last - b->pos;
     }
 
-    qs->out = *ll;
-    *ll = NULL;
+    in = ngx_quic_write_chain(pc, &qs->out, in, n, 0);
+    if (in == NGX_CHAIN_ERROR) {
+        return NGX_CHAIN_ERROR;
+    }
+
+    out = ngx_quic_read_chain(pc, &qs->out, n);
+    if (out == NGX_CHAIN_ERROR) {
+        return NGX_CHAIN_ERROR;
+    }
 
     frame = ngx_quic_alloc_frame(pc);
     if (frame == NULL) {
         return NGX_CHAIN_ERROR;
     }
 
-    while (in && ngx_buf_size(in->buf) == 0) {
-        in = in->next;
-    }
-
     frame->level = ssl_encryption_application;
     frame->type = NGX_QUIC_FT_STREAM;
     frame->data = out;
@@ -909,7 +892,9 @@ ngx_quic_stream_send_chain(ngx_connectio
 
     ngx_quic_queue_frame(qc, frame);
 
-    wev->ready = (n < flow) ? 1 : 0;
+    if (in) {
+        wev->ready = 0;
+    }
 
     ngx_log_debug1(NGX_LOG_DEBUG_EVENT, c->log, 0,
                    "quic send_chain sent:%uz", n);
@@ -1113,9 +1098,9 @@ ngx_quic_handle_stream_frame(ngx_connect
         qs->final_size = last;
     }
 
-    if (ngx_quic_order_bufs(c, &qs->in, frame->data, f->length,
-                            f->offset - qs->recv_offset)
-        != NGX_OK)
+    if (ngx_quic_write_chain(c, &qs->in, frame->data, f->length,
+                             f->offset - qs->recv_offset)
+        == NGX_CHAIN_ERROR)
     {
         return NGX_ERROR;
     }