Remove strlen usage by using a fixed buffer

Author: WyattBlue

av/subtitles/codeccontext.py

@@ -6,7 +6,7 @@
 from cython.cimports.av.packet import Packet
 from cython.cimports.av.subtitles.subtitle import SubtitleProxy, SubtitleSet
 from cython.cimports.cpython.bytes import PyBytes_FromStringAndSize
-from cython.cimports.libc.string import memcpy, strlen
+from cython.cimports.libc.string import memcpy
 
 
 @cython.cclass
@@ -65,35 +65,19 @@ def encode_subtitle(self, subtitle: SubtitleSet) -> Packet:
 
         self.open(strict=False)
 
-        # Calculate buffer size from subtitle text length
-        buf_size: cython.size_t = 0
-        i: cython.uint
-        for i in range(subtitle.proxy.struct.num_rects):
-            rect = subtitle.proxy.struct.rects[i]
-            if rect.ass != cython.NULL:
-                buf_size += strlen(rect.ass)
-            if rect.text != cython.NULL:
-                buf_size += strlen(rect.text)
-        buf_size += 1024  # padding for format overhead
-
-        buf: cython.p_uchar = cython.cast(cython.p_uchar, lib.av_malloc(buf_size))
-        if buf == cython.NULL:
-            raise MemoryError("Failed to allocate subtitle encode buffer")
+        packet: Packet = Packet(1024 * 1024)
 
         ret: cython.int = lib.avcodec_encode_subtitle(
             self.ptr,
-            buf,
-            buf_size,
+            packet.ptr.data,
+            packet.ptr.size,
             cython.address(subtitle.proxy.struct),
         )
 
         if ret < 0:
-            lib.av_free(buf)
             err_check(ret, "avcodec_encode_subtitle()")
 
-        packet: Packet = Packet(ret)
-        memcpy(packet.ptr.data, buf, ret)
-        lib.av_free(buf)
+        packet.ptr.size = ret
 
         packet.ptr.pts = subtitle.proxy.struct.pts
         packet.ptr.dts = subtitle.proxy.struct.pts