Merge pull request #4023 from Feoramund/simd-index

Vectorize `index_byte`

tests/core/bytes/test_core_bytes.odin

@@ -0,0 +1,89 @@
+package test_core_bytes
+
+import "core:bytes"
+import "core:slice"
+import "core:testing"
+
+@private SIMD_SCAN_WIDTH :: 8 * size_of(uintptr)
+
+@test
+test_index_byte_sanity :: proc(t: ^testing.T) {
+	// We must be able to find the byte at the correct index.
+	data := make([]u8, 2 * SIMD_SCAN_WIDTH)
+	defer delete(data)
+	slice.fill(data, '-')
+
+	INDEX_MAX :: SIMD_SCAN_WIDTH - 1
+
+	for offset in 0..<INDEX_MAX {
+		for idx in 0..<INDEX_MAX {
+			sub := data[offset:]
+			sub[idx] = 'o'
+			if !testing.expect_value(t, bytes.index_byte(sub, 'o'), idx) {
+				return
+			}
+			if !testing.expect_value(t, bytes.last_index_byte(sub, 'o'), idx) {
+				return
+			}
+			sub[idx] = '-'
+		}
+	}
+}
+
+@test
+test_index_byte_empty :: proc(t: ^testing.T) {
+	a: [1]u8
+	testing.expect_value(t, bytes.index_byte(a[0:0], 'o'), -1)
+	testing.expect_value(t, bytes.last_index_byte(a[0:0], 'o'), -1)
+}
+
+@test
+test_index_byte_multiple_hits :: proc(t: ^testing.T) {
+	for n in 5..<256 {
+		data := make([]u8, n)
+		defer delete(data)
+		slice.fill(data, '-')
+
+		data[n-1] = 'o'
+		data[n-3] = 'o'
+		data[n-5] = 'o'
+
+		// Find the first one.
+		if !testing.expect_value(t, bytes.index_byte(data, 'o'), n-5) {
+			return
+		}
+
+		// Find the last one.
+		if !testing.expect_value(t, bytes.last_index_byte(data, 'o'), n-1) {
+			return
+		}
+	}
+}
+
+@test
+test_index_byte_zero :: proc(t: ^testing.T) {
+	// This test protects against false positives in uninitialized memory.
+	for n in 1..<256 {
+		data := make([]u8, n + 64)
+		defer delete(data)
+		slice.fill(data, '-')
+
+		// Positive hit.
+		data[n-1] = 0
+		if !testing.expect_value(t, bytes.index_byte(data[:n], 0), n-1) {
+			return
+		}
+		if !testing.expect_value(t, bytes.last_index_byte(data[:n], 0), n-1) {
+			return
+		}
+
+		// Test for false positives.
+		data[n-1] = '-'
+		if !testing.expect_value(t, bytes.index_byte(data[:n], 0), -1) {
+			return
+		}
+		if !testing.expect_value(t, bytes.last_index_byte(data[:n], 0), -1) {
+			return
+		}
+	}
+}

tests/core/normal.odin

@@ -9,6 +9,7 @@ download_assets :: proc() {
 	}
 }
 
+@(require) import "bytes"
 @(require) import "c/libc"
 @(require) import "compress"
 @(require) import "container"