crypto/sha256: add WriteString and WriteByte method

This can reduce allocations when hashing a string or byte
rather than []byte.

For #38776

Change-Id: I1c6dd1bc018220784a05939e92b47558c0562110
Reviewed-on: https://go-review.googlesource.com/c/go/+/481478
Reviewed-by: Joel Sing <joel@sing.id.au>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>

src/crypto/internal/boring/sha.go

@@ -263,6 +263,20 @@ func (h *sha256Hash) Write(p []byte) (int, error) {
 	return len(p), nil
 }
 
+func (h *sha256Hash) WriteString(s string) (int, error) {
+	if len(s) > 0 && C._goboringcrypto_SHA256_Update(h.noescapeCtx(), unsafe.Pointer(unsafe.StringData(s)), C.size_t(len(s))) == 0 {
+		panic("boringcrypto: SHA256_Update failed")
+	}
+	return len(s), nil
+}
+
+func (h *sha256Hash) WriteByte(c byte) error {
+	if C._goboringcrypto_SHA256_Update(h.noescapeCtx(), unsafe.Pointer(&c), 1) == 0 {
+		panic("boringcrypto: SHA256_Update failed")
+	}
+	return nil
+}
+
 func (h0 *sha256Hash) sum(dst []byte) []byte {
 	h := *h0 // make copy so future Write+Sum is valid
 	if C._goboringcrypto_SHA256_Final((*C.uint8_t)(noescape(unsafe.Pointer(&h.out[0]))), h.noescapeCtx()) == 0 {

src/crypto/sha256/sha256.go

@@ -177,18 +177,10 @@ func (d *digest) Size() int {
 func (d *digest) BlockSize() int { return BlockSize }
 
 func (d *digest) Write(p []byte) (nn int, err error) {
-	boring.Unreachable()
 	nn = len(p)
 	d.len += uint64(nn)
-	if d.nx > 0 {
+	n := fillChunk(d, p)
-		n := copy(d.x[d.nx:], p)
-		d.nx += n
-		if d.nx == chunk {
-			block(d, d.x[:])
-			d.nx = 0
-		}
 	p = p[n:]
-	}
 	if len(p) >= chunk {
 		n := len(p) &^ (chunk - 1)
 		block(d, p[:n])
@@ -200,6 +192,55 @@ func (d *digest) Write(p []byte) (nn int, err error) {
 	return
 }
 
+func (d *digest) WriteString(p string) (nn int, err error) {
+	nn = len(p)
+	d.len += uint64(nn)
+	n := fillChunk(d, p)
+
+	// This duplicates the code in Write, except that it calls
+	// blockString rather than block. It would be nicer to pass
+	// in a func, but as of this writing (Go 1.20) that causes
+	// memory allocations that we want to avoid.
+
+	p = p[n:]
+	if len(p) >= chunk {
+		n := len(p) &^ (chunk - 1)
+		blockString(d, p[:n])
+		p = p[n:]
+	}
+	if len(p) > 0 {
+		d.nx = copy(d.x[:], p)
+	}
+	return
+}
+
+// fillChunk fills the remainder of the current chunk, if any.
+func fillChunk[S []byte | string](d *digest, p S) int {
+	boring.Unreachable()
+	if d.nx == 0 {
+		return 0
+	}
+	n := copy(d.x[d.nx:], p)
+	d.nx += n
+	if d.nx == chunk {
+		block(d, d.x[:])
+		d.nx = 0
+	}
+	return n
+}
+
+func (d *digest) WriteByte(c byte) error {
+	boring.Unreachable()
+	d.len++
+	d.x[d.nx] = c
+	d.nx++
+	if d.nx == chunk {
+		block(d, d.x[:])
+		d.nx = 0
+	}
+	return nil
+}
+
 func (d *digest) Sum(in []byte) []byte {
 	boring.Unreachable()
 	// Make a copy of d so that caller can keep writing and summing.

src/crypto/sha256/sha256_test.go

@@ -113,6 +113,14 @@ func TestGolden(t *testing.T) {
 			}
 			c.Reset()
 		}
+		bw := c.(io.ByteWriter)
+		for i := 0; i < len(g.in); i++ {
+			bw.WriteByte(g.in[i])
+		}
+		s = fmt.Sprintf("%x", c.Sum(nil))
+		if s != g.out {
+			t.Errorf("sha256[WriteByte](%s) = %s want %s", g.in, s, g.out)
+		}
 	}
 	for i := 0; i < len(golden224); i++ {
 		g := golden224[i]
@@ -297,7 +305,8 @@ func TestAllocations(t *testing.T) {
 	if boring.Enabled {
 		t.Skip("BoringCrypto doesn't allocate the same way as stdlib")
 	}
-	in := []byte("hello, world!")
+	const ins = "hello, world!"
+	in := []byte(ins)
 	out := make([]byte, 0, Size)
 	h := New()
 	n := int(testing.AllocsPerRun(10, func() {
@@ -308,6 +317,28 @@ func TestAllocations(t *testing.T) {
 	if n > 0 {
 		t.Errorf("allocs = %d, want 0", n)
 	}
+
+	sw := h.(io.StringWriter)
+	n = int(testing.AllocsPerRun(10, func() {
+		h.Reset()
+		sw.WriteString(ins)
+		out = h.Sum(out[:0])
+	}))
+	if n > 0 {
+		t.Errorf("string allocs = %d, want 0", n)
+	}
+
+	bw := h.(io.ByteWriter)
+	n = int(testing.AllocsPerRun(10, func() {
+		h.Reset()
+		for _, b := range in {
+			bw.WriteByte(b)
+		}
+		out = h.Sum(out[:0])
+	}))
+	if n > 0 {
+		t.Errorf("byte allocs = %d, want 0", n)
+	}
 }
 
 type cgoData struct {

src/crypto/sha256/sha256block.go

@@ -77,7 +77,7 @@ var _K = []uint32{
 	0xc67178f2,
 }
 
-func blockGeneric(dig *digest, p []byte) {
+func blockGeneric[S []byte | string](dig *digest, p S) {
 	var w [64]uint32
 	h0, h1, h2, h3, h4, h5, h6, h7 := dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4], dig.h[5], dig.h[6], dig.h[7]
 	for len(p) >= chunk {

src/crypto/sha256/sha256block_386.s

@@ -141,9 +141,9 @@
 	MSGSCHEDULE1(index); \
 	SHA256ROUND(index, const, a, b, c, d, e, f, g, h)
 
-TEXT ·block(SB),0,$296-16
+TEXT ·doBlock(SB),0,$296-12
-	MOVL	p_base+4(FP), SI
+	MOVL	p+4(FP), SI
-	MOVL	p_len+8(FP), DX
+	MOVL	n+8(FP), DX
 	SHRL	$6, DX
 	SHLL	$6, DX
 

src/crypto/sha256/sha256block_amd64.s

@@ -619,14 +619,14 @@
 	SHA256RNDS2		msg, state1, state0		\
 	sha256Msg1		(m,a)
 
-TEXT ·block(SB), 0, $536-32
+TEXT ·doBlock(SB), 0, $536-24
 	CMPB	·useSHA(SB), $1
 	JE	sha_ni
 	CMPB	·useAVX2(SB), $1
 	JE	avx2
 
-	MOVQ p_base+8(FP), SI
+	MOVQ p+8(FP), SI
-	MOVQ p_len+16(FP), DX
+	MOVQ n+16(FP), DX
 	SHRQ $6, DX
 	SHLQ $6, DX
 
@@ -741,8 +741,8 @@ end:
 
 avx2:
 	MOVQ dig+0(FP), CTX          // d.h[8]
-	MOVQ p_base+8(FP), INP
+	MOVQ p+8(FP), INP
-	MOVQ p_len+16(FP), NUM_BYTES
+	MOVQ n+16(FP), NUM_BYTES
 
 	LEAQ -64(INP)(NUM_BYTES*1), NUM_BYTES // Pointer to the last block
 	MOVQ NUM_BYTES, _INP_END(SP)
@@ -935,8 +935,8 @@ done_hash:
 
 sha_ni:
 	MOVQ		dig+0(FP), digestPtr		// init digest hash vector H0, H1,..., H7 pointer
-	MOVQ		p_base+8(FP), dataPtr		// init input data base pointer
+	MOVQ		p+8(FP), dataPtr		// init input data base pointer
-	MOVQ		p_len+16(FP), numBytes		// get number of input bytes to hash
+	MOVQ		n+16(FP), numBytes		// get number of input bytes to hash
 	SHRQ		$6, numBytes			// force modulo 64 input buffer length
 	SHLQ		$6, numBytes
 	CMPQ		numBytes, $0			// exit early for zero-length input buffer

src/crypto/sha256/sha256block_arm64.go

@@ -4,18 +4,30 @@
 
 package sha256
 
-import "internal/cpu"
+import (
+	"internal/cpu"
+	"unsafe"
+)
 
 var k = _K
 
 //go:noescape
-func sha256block(h []uint32, p []byte, k []uint32)
+func sha256block(h []uint32, p *byte, n int, k []uint32)
 
 func block(dig *digest, p []byte) {
 	if !cpu.ARM64.HasSHA2 {
 		blockGeneric(dig, p)
 	} else {
 		h := dig.h[:]
-		sha256block(h, p, k)
+		sha256block(h, unsafe.SliceData(p), len(p), k)
+	}
+}
+
+func blockString(dig *digest, s string) {
+	if !cpu.ARM64.HasSHA2 {
+		blockGeneric(dig, s)
+	} else {
+		h := dig.h[:]
+		sha256block(h, unsafe.StringData(s), len(s), k)
 	}
 }

src/crypto/sha256/sha256block_arm64.s

@@ -9,12 +9,12 @@
 	SHA256H2	V9.S4, V8, V3 \
 	VMOV	V2.B16, V8.B16
 
-// func sha256block(h []uint32, p []byte, k []uint32)
+// func sha256block(h []uint32, p *byte, n int, k []uint32)
 TEXT ·sha256block(SB),NOSPLIT,$0
 	MOVD	h_base+0(FP), R0                           // Hash value first address
-	MOVD	p_base+24(FP), R1                          // message first address
+	MOVD	p+24(FP), R1                               // message first address
-	MOVD	k_base+48(FP), R2                          // k constants first address
+	MOVD	k_base+40(FP), R2                          // k constants first address
-	MOVD	p_len+32(FP), R3                           // message length
+	MOVD	n+32(FP), R3	                           // message length
 	VLD1	(R0), [V0.S4, V1.S4]                       // load h(a,b,c,d,e,f,g,h)
 	VLD1.P	64(R2), [V16.S4, V17.S4, V18.S4, V19.S4]
 	VLD1.P	64(R2), [V20.S4, V21.S4, V22.S4, V23.S4]

src/crypto/sha256/sha256block_decl.go

@@ -6,5 +6,15 @@
 
 package sha256
 
+import "unsafe"
+
 //go:noescape
-func block(dig *digest, p []byte)
+func doBlock(dig *digest, p *byte, n int)
+
+func block(dig *digest, p []byte) {
+	doBlock(dig, unsafe.SliceData(p), len(p))
+}
+
+func blockString(dig *digest, s string) {
+	doBlock(dig, unsafe.StringData(s), len(s))
+}

src/crypto/sha256/sha256block_generic.go

@@ -9,3 +9,7 @@ package sha256
 func block(dig *digest, p []byte) {
 	blockGeneric(dig, p)
 }
+
+func blockString(dig *digest, s string) {
+	blockGeneric(dig, s)
+}

src/crypto/sha256/sha256block_ppc64x.s

@@ -284,11 +284,11 @@ GLOBL ·kcon(SB), RODATA, $1088
 #define VPERMLE(va,vb,vc,vt)
 #endif
 
-// func block(dig *digest, p []byte)
+// func doBlock(dig *digest, p []byte)
-TEXT ·block(SB),0,$0-32
+TEXT ·doBlock(SB),0,$0-24
 	MOVD	dig+0(FP), CTX
-	MOVD	p_base+8(FP), INP
+	MOVD	p+8(FP), INP
-	MOVD	p_len+16(FP), LEN
+	MOVD	n+16(FP), LEN
 
 	SRD	$6, LEN
 	SLD	$6, LEN

src/crypto/sha256/sha256block_s390x.go

@@ -4,6 +4,13 @@
 
 package sha256
 
-import "internal/cpu"
+import (
+	"internal/cpu"
+	"unsafe"
+)
 
 var useAsm = cpu.S390X.HasSHA256
+
+func doBlockGeneric(dig *digest, p *byte, n int) {
+	blockGeneric(dig, unsafe.String(p, n))
+}

src/crypto/sha256/sha256block_s390x.s

@@ -4,10 +4,10 @@
 
 #include "textflag.h"
 
-// func block(dig *digest, p []byte)
+// func doBlock(dig *digest, p *byte, n int)
-TEXT ·block(SB), NOSPLIT|NOFRAME, $0-32
+TEXT ·doBlock(SB), NOSPLIT|NOFRAME, $0-24
 	MOVBZ  ·useAsm(SB), R4
-	LMG    dig+0(FP), R1, R3            // R2 = &p[0], R3 = len(p)
+	LMG    dig+0(FP), R1, R3            // R2 = p, R3 = n
 	MOVBZ  $2, R0                       // SHA-256 function code
 	CMPBEQ R4, $0, generic
 
@@ -17,4 +17,4 @@ loop:
 	RET
 
 generic:
-	BR ·blockGeneric(SB)
+	BR ·doBlockGeneric(SB)