[feature] support processing of (many) more media types (#3090)

* initial work replacing our media decoding / encoding pipeline with ffprobe + ffmpeg

* specify the video codec to use when generating static image from emoji

* update go-storage library (fixes incompatibility after updating go-iotools)

* maintain image aspect ratio when generating a thumbnail for it

* update readme to show go-ffmpreg

* fix a bunch of media tests, move filesize checking to callers of media manager for more flexibility

* remove extra debug from error message

* fix up incorrect function signatures

* update PutFile to just use regular file copy, as changes are file is on separate partition

* fix remaining tests, remove some unneeded tests now we're working with ffmpeg/ffprobe

* update more tests, add more code comments

* add utilities to generate processed emoji / media outputs

* fix remaining tests

* add test for opus media file, add license header to utility cmds

* limit the number of concurrently available ffmpeg / ffprobe instances

* reduce number of instances

* further reduce number of instances

* fix envparsing test with configuration variables

* update docs and configuration with new media-{local,remote}-max-size variables

vendor/codeberg.org/gruf/go-ffmpreg/util/wasm.go

@@ -0,0 +1,81 @@
+package util
+
+import (
+	"bytes"
+	"context"
+
+	"github.com/tetratelabs/wazero/api"
+)
+
+// NOTE:
+// the below functions are not very well optimized
+// for repeated calls. this is relying on the fact
+// that the only place they get used (tempnam), is
+// not called very often, should only be once per run
+// so calls to ExportedFunction() and Call() instead
+// of caching api.Function and using CallWithStack()
+// will work out the same (if only called once).
+
+// maxaddr is the maximum
+// wasm32 memory address.
+const maxaddr = ^uint32(0)
+
+func malloc(ctx context.Context, mod api.Module, sz uint32) uint32 {
+	stack, err := mod.ExportedFunction("malloc").Call(ctx, uint64(sz))
+	if err != nil {
+		panic(err)
+	}
+	ptr := api.DecodeU32(stack[0])
+	if ptr == 0 {
+		panic("out of memory")
+	}
+	return ptr
+}
+
+func free(ctx context.Context, mod api.Module, ptr uint32) {
+	if ptr != 0 {
+		mod.ExportedFunction("free").Call(ctx, uint64(ptr))
+	}
+}
+
+func view(ctx context.Context, mod api.Module, ptr uint32, n uint32) []byte {
+	if n == 0 {
+		n = maxaddr - ptr
+	}
+	mem := mod.Memory()
+	b, ok := mem.Read(ptr, n)
+	if !ok {
+		panic("out of range")
+	}
+	return b
+}
+
+func read(ctx context.Context, mod api.Module, ptr, n uint32) []byte {
+	return bytes.Clone(view(ctx, mod, ptr, n))
+}
+
+func readString(ctx context.Context, mod api.Module, ptr, n uint32) string {
+	return string(view(ctx, mod, ptr, n))
+}
+
+func write(ctx context.Context, mod api.Module, b []byte) uint32 {
+	mem := mod.Memory()
+	len := uint32(len(b))
+	ptr := malloc(ctx, mod, len)
+	ok := mem.Write(ptr, b)
+	if !ok {
+		panic("out of range")
+	}
+	return ptr
+}
+
+func writeString(ctx context.Context, mod api.Module, str string) uint32 {
+	mem := mod.Memory()
+	len := uint32(len(str) + 1)
+	ptr := malloc(ctx, mod, len)
+	ok := mem.WriteString(ptr, str)
+	if !ok {
+		panic("out of range")
+	}
+	return ptr
+}