[experiment] add alternative wasm sqlite3 implementation available via build-tag (#2863)

This allows for building GoToSocial with [SQLite transpiled to WASM](https://github.com/ncruces/go-sqlite3) and accessed through [Wazero](https://wazero.io/).

1 files changed, 76 insertions, 0 deletions

diff --git a/vendor/github.com/tetratelabs/wazero/internal/platform/mmap_linux.go b/vendor/github.com/tetratelabs/wazero/internal/platform/mmap_linux.go
new file mode 100644
index 000000000..55906e827
--- /dev/null
+++ b/vendor/github.com/tetratelabs/wazero/internal/platform/mmap_linux.go
@@ -0,0 +1,76 @@
+package platform
+
+import (
+	"math/bits"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+	"syscall"
+)
+
+const (
+	// https://man7.org/linux/man-pages/man2/mmap.2.html
+	__MAP_HUGE_SHIFT = 26
+	__MAP_HUGETLB    = 0x40000
+)
+
+var hugePagesConfigs []hugePagesConfig
+
+type hugePagesConfig struct {
+	size int
+	flag int
+}
+
+func (hpc *hugePagesConfig) match(size int) bool {
+	return (size & (hpc.size - 1)) == 0
+}
+
+func init() {
+	dirents, err := os.ReadDir("/sys/kernel/mm/hugepages/")
+	if err != nil {
+		return
+	}
+
+	for _, dirent := range dirents {
+		name := dirent.Name()
+		if !strings.HasPrefix(name, "hugepages-") {
+			continue
+		}
+		if !strings.HasSuffix(name, "kB") {
+			continue
+		}
+		n, err := strconv.ParseUint(name[10:len(name)-2], 10, 64)
+		if err != nil {
+			continue
+		}
+		if bits.OnesCount64(n) != 1 {
+			continue
+		}
+		n *= 1024
+		hugePagesConfigs = append(hugePagesConfigs, hugePagesConfig{
+			size: int(n),
+			flag: int(bits.TrailingZeros64(n)<<__MAP_HUGE_SHIFT) | __MAP_HUGETLB,
+		})
+	}
+
+	sort.Slice(hugePagesConfigs, func(i, j int) bool {
+		return hugePagesConfigs[i].size > hugePagesConfigs[j].size
+	})
+}
+
+func mmapCodeSegment(size, prot int) ([]byte, error) {
+	flags := syscall.MAP_ANON | syscall.MAP_PRIVATE
+
+	for _, hugePagesConfig := range hugePagesConfigs {
+		if hugePagesConfig.match(size) {
+			b, err := syscall.Mmap(-1, 0, size, prot, flags|hugePagesConfig.flag)
+			if err != nil {
+				continue
+			}
+			return b, nil
+		}
+	}
+
+	return syscall.Mmap(-1, 0, size, prot, flags)
+}