From 855a8c0cd9c79d3e708d037811b04a821f95a5bc Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Fri, 15 Jan 2021 18:18:07 -0800
Subject: [PATCH] Don't assume the ring buffer's read vector is the next
 writable space

This is untrue since the ring buffer leaves one element unwritten, so there's
one extra element to be written once a readable element is read.
---
 alc/backends/opensl.cpp | 76 ++++++++++++++++++++++-------------------
 1 file changed, 41 insertions(+), 35 deletions(-)

diff --git a/alc/backends/opensl.cpp b/alc/backends/opensl.cpp
index 8d966fca..f6e7fddb 100644
--- a/alc/backends/opensl.cpp
+++ b/alc/backends/opensl.cpp
@@ -868,6 +868,36 @@ void OpenSLCapture::stop()
 
 void OpenSLCapture::captureSamples(al::byte *buffer, uint samples)
 {
+    const uint update_size{mDevice->UpdateSize};
+    const uint chunk_size{update_size * mFrameSize};
+
+    /* Read the desired samples from the ring buffer then advance its read
+     * pointer.
+     */
+    auto rdata = mRing->getReadVector();
+    for(uint i{0};i < samples;)
+    {
+        const uint rem{minu(samples - i, update_size - mSplOffset)};
+        std::copy_n(rdata.first.buf + mSplOffset*mFrameSize, rem*mFrameSize,
+            buffer + i*mFrameSize);
+
+        mSplOffset += rem;
+        if(mSplOffset == update_size)
+        {
+            /* Finished a chunk, reset the offset and advance the read pointer. */
+            mSplOffset = 0;
+            mRing->readAdvance(1);
+
+            rdata.first.len -= 1;
+            if(!rdata.first.len)
+                rdata.first = rdata.second;
+            else
+                rdata.first.buf += chunk_size;
+        }
+
+        i += rem;
+    }
+
     SLAndroidSimpleBufferQueueItf bufferQueue{};
     if LIKELY(mDevice->Connected.load(std::memory_order_acquire))
     {
@@ -881,44 +911,20 @@ void OpenSLCapture::captureSamples(al::byte *buffer, uint samples)
         }
     }
 
-    const uint update_size{mDevice->UpdateSize};
-    const uint chunk_size{update_size * mFrameSize};
-
-    /* Read the desired samples from the ring buffer then advance its read
-     * pointer.
-     */
-    auto data = mRing->getReadVector();
-    for(uint i{0};i < samples;)
+    if LIKELY(bufferQueue)
     {
-        const uint rem{minu(samples - i, update_size - mSplOffset)};
-        std::copy_n(data.first.buf + mSplOffset*mFrameSize, rem*mFrameSize, buffer + i*mFrameSize);
-
-        mSplOffset += rem;
-        if(mSplOffset == update_size)
+        SLresult result{SL_RESULT_SUCCESS};
+        auto wdata = mRing->getWriteVector();
+        for(size_t i{0u};i < wdata.first.len && SL_RESULT_SUCCESS == result;i++)
         {
-            /* Finished a chunk, reset the offset and advance the read pointer. */
-            mSplOffset = 0;
-            mRing->readAdvance(1);
-
-            if LIKELY(bufferQueue)
-            {
-                const SLresult result{VCALL(bufferQueue,Enqueue)(data.first.buf, chunk_size)};
-                PRINTERR(result, "bufferQueue->Enqueue");
-                if UNLIKELY(SL_RESULT_SUCCESS != result)
-                {
-                    mDevice->handleDisconnect("Failed to update capture buffer: 0x%08x", result);
-                    bufferQueue = nullptr;
-                }
-            }
-
-            data.first.len--;
-            if(!data.first.len)
-                data.first = data.second;
-            else
-                data.first.buf += chunk_size;
+            result = VCALL(bufferQueue,Enqueue)(wdata.first.buf + chunk_size*i, chunk_size);
+            PRINTERR(result, "bufferQueue->Enqueue");
+        }
+        for(size_t i{0u};i < wdata.second.len && SL_RESULT_SUCCESS == result;i++)
+        {
+            result = VCALL(bufferQueue,Enqueue)(wdata.second.buf + chunk_size*i, chunk_size);
+            PRINTERR(result, "bufferQueue->Enqueue");
         }
-
-        i += rem;
     }
 }