Use .first(n) consistently rather than slice(0, n)

src/workerd/api/actor-state.c++

@@ -1010,7 +1010,7 @@ jsg::JsValue deserializeV8Value(
       kj::String actorId = getCurrentActorId().orDefault([]() { return kj::String(); });
       KJ_FAIL_ASSERT("actor storage deserialization failed", "failed to deserialize stored value",
           actorId, exception.getHandle(js), key, buf.size(),
-          buf.slice(0, std::min(static_cast<size_t>(3), buf.size())));
+          buf.first(std::min(static_cast<size_t>(3), buf.size())));
     });
   } catch (jsg::JsExceptionThrown&) {
     // We can occasionally hit an isolate termination here -- we prefix the error with jsg to avoid

src/workerd/api/crypto/aes.c++

@@ -300,7 +300,7 @@ private:
       plainSize = 0;
     }
 
-    auto actualCipherText = cipherText.slice(0, cipherText.size() - tagLength / 8);
+    auto actualCipherText = cipherText.first(cipherText.size() - tagLength / 8);
     auto tagText = cipherText.slice(actualCipherText.size(), cipherText.size());
 
     auto plainText = kj::heapArray<kj::byte>(actualCipherText.size());
@@ -513,7 +513,7 @@ protected:
     // counter portion of the block back to zero.
     auto inputSizePart1 = BN_get_word(numBlocksUntilReset.get()) * AES_BLOCK_SIZE;
 
-    process(&cipher, data.slice(0, inputSizePart1), counter, result.asPtr());
+    process(&cipher, data.first(inputSizePart1), counter, result.asPtr());
 
     // Zero the counter bits of the block. Chromium creates a copy but we own our buffer.
     {

src/workerd/api/crypto/digest.c++

@@ -72,7 +72,7 @@ private:
 
     if (format == "jwk") {
       // This assert enforces that the slice logic to fill in `.alg` below is safe.
-      JSG_REQUIRE(keyAlgorithm.hash.name.slice(0, 4) == "SHA-"_kj, DOMNotSupportedError,
+      JSG_REQUIRE(keyAlgorithm.hash.name.first(4) == "SHA-"_kj, DOMNotSupportedError,
           "Unimplemented JWK key export format for key algorithm \"", keyAlgorithm.hash.name,
           "\".");
 

src/workerd/api/crypto/ec.c++

@@ -338,7 +338,7 @@ public:
       return nullptr;
     }
 
-    auto r = signature.slice(0, rsSize);
+    auto r = signature.first(rsSize);
     auto s = signature.slice(rsSize, signature.size());
 
     // Trim leading zeros.

src/workerd/api/crypto/keys.c++

@@ -255,7 +255,7 @@ kj::Array<kj::byte> AsymmetricKeyCryptoKeyImpl::sign(
 
   KJ_ASSERT(signatureSize <= signature.size());
   if (signatureSize < signature.size()) {
-    signature = kj::heapArray<kj::byte>(signature.slice(0, signatureSize));
+    signature = kj::heapArray<kj::byte>(signature.first(signatureSize));
   }
 
   return signatureSslToWebCrypto(kj::mv(signature));

src/workerd/api/crypto/rsa.c++

@@ -168,7 +168,7 @@ kj::Array<kj::byte> Rsa::sign(const kj::ArrayPtr<const kj::byte> data) const {
     // We did not fill the entire buffer, let's make sure we zero
     // out the rest of it so we don't leak any uninitialized data.
     signature.slice(signatureSize).fill(0);
-    return signature.slice(0, signatureSize).attach(kj::mv(signature));
+    return signature.first(signatureSize).attach(kj::mv(signature));
   }
 
   return kj::mv(signature);

src/workerd/api/eventsource.c++

@@ -48,7 +48,7 @@ public:
       KJ_IF_SOME(found, findEndOfLine(input)) {
         auto prefix = kept.releaseAsArray();
         // Feed the line into the processor.
-        feed(kj::str(prefix, input.slice(0, found.pos)));
+        feed(kj::str(prefix, input.first(found.pos)));
         input = found.remaining;
         // If we've reached the end of the input, input will == nullptr here.
       } else {
@@ -168,7 +168,7 @@ private:
       };
 
       KJ_IF_SOME(pos, line.findFirst(':')) {
-        handle(*this, line.slice(0, pos), line.slice(pos + 1));
+        handle(*this, line.first(pos), line.slice(pos + 1));
       } else {
         handle(*this, line, ""_kjc);
       }

src/workerd/api/form-data.c++

@@ -122,7 +122,7 @@ void parseFormData(kj::Maybe<jsg::Lock&> js,
     //
     // TODO(soon): Read the Content-Type to support files.
 
-    auto headersText = kj::str(body.slice(0, match[0].second - body.begin()));
+    auto headersText = kj::str(body.first(match[0].second - body.begin()));
     body = body.slice(match[0].second - body.begin(), body.size());
 
     kj::HttpHeaders headers(*formDataHeaderTable.table);
@@ -163,7 +163,7 @@ void parseFormData(kj::Maybe<jsg::Lock&> js,
 
     if (message.size() > 0) {
       // If we skipped a CR, we must avoid including it in the message data.
-      message = message.slice(0, message.size() - uint(message.back() == '\r'));
+      message = message.first(message.size() - uint(message.back() == '\r'));
     }
 
     if (filename == kj::none || convertFilesToStrings) {

src/workerd/api/global-scope.c++

@@ -675,7 +675,7 @@ jsg::JsString ServiceWorkerGlobalScope::btoa(jsg::Lock& js, jsg::JsValue data) {
   auto result = kj::heapArray<kj::byte>(expected_length);
   auto written = simdutf::binary_to_base64(
       strArray.asChars().begin(), strArray.size(), result.asChars().begin());
-  return js.str(result.slice(0, written).attach(kj::mv(result)));
+  return js.str(result.first(written).attach(kj::mv(result)));
 }
 jsg::JsString ServiceWorkerGlobalScope::atob(jsg::Lock& js, kj::String data) {
   auto decoded = kj::decodeBase64(data.asArray());

src/workerd/api/http.c++

@@ -85,7 +85,7 @@ jsg::ByteString normalizeHeaderValue(jsg::ByteString value) {
     slice = slice.slice(1, slice.size());
   }
   while (slice.size() > 0 && isHttpWhitespace(slice.back())) {
-    slice = slice.slice(0, slice.size() - 1);
+    slice = slice.first(slice.size() - 1);
   }
   if (slice.size() == value.size()) {
     return kj::mv(value);

src/workerd/api/http.h

@@ -293,7 +293,7 @@ class Body: public jsg::Object {
         : ownBytes(kj::refcounted<RefcountedBytes>(string.releaseArray().releaseAsBytes())),
           view([this] {
             auto bytesIncludingNull = ownBytes.get<kj::Own<RefcountedBytes>>()->bytes.asPtr();
-            return bytesIncludingNull.slice(0, bytesIncludingNull.size() - 1);
+            return bytesIncludingNull.first(bytesIncludingNull.size() - 1);
           }()) {}
     Buffer(jsg::Ref<Blob> blob)
         : ownBytes(kj::mv(blob)),

src/workerd/api/node/buffer.c++

@@ -40,7 +40,7 @@ kj::Array<byte> decodeHexTruncated(kj::ArrayPtr<kj::byte> text, bool strict = fa
     if (strict) {
       JSG_FAIL_REQUIRE(TypeError, "The text is not valid hex");
     }
-    text = text.slice(0, text.size() - 1);
+    text = text.first(text.size() - 1);
   }
   auto vec = kj::Vector<kj::byte>(text.size() / 2);
 
@@ -159,7 +159,7 @@ kj::Array<kj::byte> decodeStringImpl(
       auto len = result.written;
       auto dest = kj::heapArray<kj::byte>(nbytes::Base64DecodedSize(buf.begin(), len));
       len = nbytes::Base64Decode(dest.asChars().begin(), dest.size(), buf.begin(), buf.size());
-      return dest.slice(0, len).attach(kj::mv(dest));
+      return dest.first(len).attach(kj::mv(dest));
     }
     case Encoding::HEX: {
       KJ_STACK_ARRAY(kj::byte, buf, length, 1024, 536870888);

src/workerd/api/node/i18n.c++

@@ -60,7 +60,7 @@ kj::Maybe<kj::Array<kj::byte>> TranscodeDefault(
   ucnv_convertEx(to.conv(), from.conv(), &target, target + limit, &source_, source_ + source.size(),
       nullptr, nullptr, nullptr, nullptr, true, true, &status);
   if (U_SUCCESS(status)) {
-    return out.slice(0, target - out.asChars().begin()).attach(kj::mv(out));
+    return out.first(target - out.asChars().begin()).attach(kj::mv(out));
   }
 
   return kj::none;
@@ -82,7 +82,7 @@ kj::Maybe<kj::Array<kj::byte>> TranscodeLatin1ToUTF16(
     return kj::none;
   }
 
-  return destbuf.slice(0, actual_length).asBytes().attach(kj::mv(destbuf));
+  return destbuf.first(actual_length).asBytes().attach(kj::mv(destbuf));
 }
 
 kj::Maybe<kj::Array<kj::byte>> TranscodeFromUTF16(
@@ -105,7 +105,7 @@ kj::Maybe<kj::Array<kj::byte>> TranscodeFromUTF16(
       utf16_input.begin(), utf16_input.size(), &status);
 
   if (U_SUCCESS(status)) {
-    return destbuf.slice(0, len).asBytes().attach(kj::mv(destbuf));
+    return destbuf.first(len).asBytes().attach(kj::mv(destbuf));
   }
 
   return kj::none;

src/workerd/api/streams/internal.c++

@@ -163,7 +163,7 @@ private:
           // In which case we want to add that subset to the parts list here before we exit
           // the loop.
           if (amount > 0) {
-            parts.add(bytes.slice(0, amount).attach(kj::mv(bytes)));
+            parts.add(bytes.first(amount).attach(kj::mv(bytes)));
           }
           break;
         }

src/workerd/api/streams/standard.c++

@@ -2654,7 +2654,7 @@ public:
   jsg::Promise<kj::String> allText(jsg::Lock& js) {
     return loop(js).then(js, [this](auto& js, PartList&& partPtrs) {
       auto out = kj::heapArray<char>(runningTotal + 1);
-      copyInto(out.slice(0, out.size() - 1).asBytes(), kj::mv(partPtrs));
+      copyInto(out.first(out.size() - 1).asBytes(), kj::mv(partPtrs));
       out.back() = '\0';
       return kj::String(kj::mv(out));
     });

src/workerd/api/streams/writable.c++

@@ -469,7 +469,7 @@ public:
         KJ_DASSERT(ptr.size() > 0);
         KJ_DASSERT(piece.size() <= ptr.size());
         if (piece.size() == 0) continue;
-        ptr.slice(0, piece.size()).copyFrom(piece);
+        ptr.first(piece.size()).copyFrom(piece);
         ptr = ptr.slice(piece.size());
       }
 

src/workerd/api/url.c++

@@ -69,11 +69,11 @@ void normalizePort(kj::Url& url) {
   KJ_IF_SOME(colon, url.host.findFirst(':')) {
     if (url.host.size() == colon + 1) {
       // Remove trailing ':'.
-      url.host = kj::str(url.host.slice(0, colon));
+      url.host = kj::str(url.host.first(colon));
     } else KJ_IF_SOME(defaultPort, defaultPortForScheme(url.scheme)) {
       if (defaultPort == url.host.slice(colon + 1)) {
         // Remove scheme-default port.
-        url.host = kj::str(url.host.slice(0, colon));
+        url.host = kj::str(url.host.first(colon));
       }
     }
   }
@@ -84,7 +84,7 @@ kj::Maybe<kj::ArrayPtr<const char>> trySplit(kj::ArrayPtr<const char>& text, cha
 
   for (auto i: kj::indices(text)) {
     if (text[i] == c) {
-      kj::ArrayPtr<const char> result = text.slice(0, i);
+      kj::ArrayPtr<const char> result = text.first(i);
       text = text.slice(i + 1, text.size());
       return result;
     }
@@ -97,7 +97,7 @@ kj::ArrayPtr<const char> split(kj::StringPtr& text, const kj::parse::CharGroup_&
 
   for (auto i: kj::indices(text)) {
     if (chars.contains(text[i])) {
-      kj::ArrayPtr<const char> result = text.slice(0, i);
+      kj::ArrayPtr<const char> result = text.first(i);
       text = text.slice(i);
       return result;
     }
@@ -239,7 +239,7 @@ kj::String URL::getProtocol() {
 }
 void URL::setProtocol(kj::String value) {
   KJ_IF_SOME(colon, value.findFirst(':')) {
-    value = kj::str(value.slice(0, colon));
+    value = kj::str(value.first(colon));
   }
 
   auto copy = url->clone();
@@ -333,14 +333,14 @@ void URL::setHost(kj::String value) {
 
 kj::String URL::getHostname() {
   KJ_IF_SOME(colon, url->host.findFirst(':')) {
-    return kj::str(url->host.slice(0, colon));
+    return kj::str(url->host.first(colon));
   }
   return kj::str(url->host);
 }
 void URL::setHostname(kj::String value) {
   // In contrast to the host setter, the hostname setter explicitly ignores any new port. We take
   // the hostname from the new value and the port from the old value.
-  auto hostnameString = value.slice(0, value.findFirst(':').orDefault(value.size()));
+  auto hostnameString = value.first(value.findFirst(':').orDefault(value.size()));
   auto portString = url->host.slice(url->host.findFirst(':').orDefault(url->host.size()));
 
   url->host = kj::str(hostnameString, portString);
@@ -355,7 +355,7 @@ kj::String URL::getPort() {
 void URL::setPort(kj::String value) {
   KJ_IF_SOME(colon, url->host.findFirst(':')) {
     // Our url's host already has a port. Replace it.
-    value = kj::str(url->host.slice(0, colon + 1), kj::mv(value));
+    value = kj::str(url->host.first(colon + 1), kj::mv(value));
   } else {
     value = kj::str(url->host, ':', kj::mv(value));
   }

src/workerd/api/urlpattern.c++

@@ -197,7 +197,7 @@ kj::Maybe<URLPattern::URLPatternResult> URLPattern::exec(
         return s.asPtr();
       }))) {
         auto p = url.getProtocol();
-        protocol = kj::str(p.slice(0, p.size() - 1));
+        protocol = kj::str(p.first(p.size() - 1));
         username = kj::str(url.getUsername());
         password = kj::str(url.getPassword());
         hostname = kj::str(url.getHostname());

src/workerd/api/util.c++

@@ -19,7 +19,7 @@ kj::ArrayPtr<const char> split(kj::ArrayPtr<const char>& text, char c) {
 
   for (auto i: kj::indices(text)) {
     if (text[i] == c) {
-      kj::ArrayPtr<const char> result = text.slice(0, i);
+      kj::ArrayPtr<const char> result = text.first(i);
       text = text.slice(i + 1, text.size());
       return result;
     }
@@ -235,7 +235,7 @@ kj::Array<char16_t> fastEncodeUtf16(kj::ArrayPtr<const char> bytes) {
   auto output = kj::heapArray<char16_t>(expected_length);
   auto actual_length =
       simdutf::convert_utf8_to_utf16(bytes.asChars().begin(), bytes.size(), output.begin());
-  return output.slice(0, actual_length).attach(kj::mv(output));
+  return output.first(actual_length).attach(kj::mv(output));
 }
 
 }  // namespace workerd::api

src/workerd/io/trace.h

@@ -449,7 +449,7 @@ class WorkerTracer final: public kj::Refcounted {
 // Helper function used when setting "truncated_script_id" tags. Truncates the scriptId to 10
 // characters.
 inline kj::String truncateScriptId(kj::StringPtr id) {
-  auto truncatedId = id.slice(0, kj::min(id.size(), 10));
+  auto truncatedId = id.first(kj::min(id.size(), 10));
   return kj::str(truncatedId);
 }