From c3ccff19603c0778781fd18e0e38e55950420780 Mon Sep 17 00:00:00 2001
From: Alan Ding <alanding@google.com>
Date: Mon, 29 Apr 2024 00:44:31 -0700
Subject: ui: Refactor DisplayIdentification to use ftl::stable_hash

Replace cityHash64Len0To16 with ftl::stable_hash which can handle up to
64 bytes string instead of just up to 16.

Bug: 185536303
Bug: 194863377
Test: DisplayIdentification_test
Change-Id: I90056145033ed5798dd5f5d99884028749d5d879
---
 libs/ui/DisplayIdentification.cpp | 67 ++-------------------------------------
 1 file changed, 2 insertions(+), 65 deletions(-)

(limited to 'libs/ui/DisplayIdentification.cpp')

diff --git a/libs/ui/DisplayIdentification.cpp b/libs/ui/DisplayIdentification.cpp
index 82e5427317..0908ae85a8 100644
--- a/libs/ui/DisplayIdentification.cpp
+++ b/libs/ui/DisplayIdentification.cpp
@@ -23,67 +23,13 @@
 #include <optional>
 #include <span>
 
+#include <ftl/hash.h>
 #include <log/log.h>
-
 #include <ui/DisplayIdentification.h>
 
 namespace android {
 namespace {
 
-template <class T>
-inline T load(const void* p) {
-    static_assert(std::is_integral<T>::value, "T must be integral");
-
-    T r;
-    std::memcpy(&r, p, sizeof(r));
-    return r;
-}
-
-uint64_t rotateByAtLeast1(uint64_t val, uint8_t shift) {
-    return (val >> shift) | (val << (64 - shift));
-}
-
-uint64_t shiftMix(uint64_t val) {
-    return val ^ (val >> 47);
-}
-
-__attribute__((no_sanitize("unsigned-integer-overflow")))
-uint64_t hash64Len16(uint64_t u, uint64_t v) {
-    constexpr uint64_t kMul = 0x9ddfea08eb382d69;
-    uint64_t a = (u ^ v) * kMul;
-    a ^= (a >> 47);
-    uint64_t b = (v ^ a) * kMul;
-    b ^= (b >> 47);
-    b *= kMul;
-    return b;
-}
-
-__attribute__((no_sanitize("unsigned-integer-overflow")))
-uint64_t hash64Len0To16(const char* s, uint64_t len) {
-    constexpr uint64_t k2 = 0x9ae16a3b2f90404f;
-    constexpr uint64_t k3 = 0xc949d7c7509e6557;
-
-    if (len > 8) {
-        const uint64_t a = load<uint64_t>(s);
-        const uint64_t b = load<uint64_t>(s + len - 8);
-        return hash64Len16(a, rotateByAtLeast1(b + len, static_cast<uint8_t>(len))) ^ b;
-    }
-    if (len >= 4) {
-        const uint32_t a = load<uint32_t>(s);
-        const uint32_t b = load<uint32_t>(s + len - 4);
-        return hash64Len16(len + (a << 3), b);
-    }
-    if (len > 0) {
-        const unsigned char a = static_cast<unsigned char>(s[0]);
-        const unsigned char b = static_cast<unsigned char>(s[len >> 1]);
-        const unsigned char c = static_cast<unsigned char>(s[len - 1]);
-        const uint32_t y = static_cast<uint32_t>(a) + (static_cast<uint32_t>(b) << 8);
-        const uint32_t z = static_cast<uint32_t>(len) + (static_cast<uint32_t>(c) << 2);
-        return shiftMix(y * k2 ^ z * k3) * k2;
-    }
-    return k2;
-}
-
 using byte_view = std::span<const uint8_t>;
 
 constexpr size_t kEdidBlockSize = 128;
@@ -320,7 +266,7 @@ std::optional<Edid> parseEdid(const DisplayIdentificationData& edid) {
     // Hash model string instead of using product code or (integer) serial number, since the latter
     // have been observed to change on some displays with multiple inputs. Use a stable hash instead
     // of std::hash which is only required to be same within a single execution of a program.
-    const uint32_t modelHash = static_cast<uint32_t>(cityHash64Len0To16(modelString));
+    const uint32_t modelHash = static_cast<uint32_t>(*ftl::stable_hash(modelString));
 
     // Parse extension blocks.
     std::optional<Cea861ExtensionBlock> cea861Block;
@@ -394,13 +340,4 @@ PhysicalDisplayId getVirtualDisplayId(uint32_t id) {
     return PhysicalDisplayId::fromEdid(0, kVirtualEdidManufacturerId, id);
 }
 
-uint64_t cityHash64Len0To16(std::string_view sv) {
-    auto len = sv.length();
-    if (len > 16) {
-        ALOGE("%s called with length %zu. Only hashing the first 16 chars", __FUNCTION__, len);
-        len = 16;
-    }
-    return hash64Len0To16(sv.data(), len);
-}
-
 } // namespace android
-- 
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