Implement simple JSON serializer (#411)

* Implement simple JSON serializer

* CR feedback

* Add debug assertion to `append_string_unchecked`

aws/sdk/build.gradle.kts

@@ -19,7 +19,7 @@ plugins {
 val smithyVersion: String by project
 
 val sdkOutputDir = buildDir.resolve("aws-sdk")
-val runtimeModules = listOf("smithy-types", "smithy-xml", "smithy-http", "smithy-http-tower", "protocol-test-helpers")
+val runtimeModules = listOf("smithy-types", "smithy-json", "smithy-xml", "smithy-http", "smithy-http-tower", "protocol-test-helpers")
 val awsModules = listOf("aws-auth", "aws-endpoint", "aws-types", "aws-hyper", "aws-sig-auth", "aws-http")
 
 buildscript {

rust-runtime/inlineable/Cargo.toml

@@ -14,6 +14,7 @@ are to allow this crate to be compilable and testable in isolation, no client co
 "http" = "0.2.1"
 "smithy-types" = { version = "0.0.1", path = "../smithy-types" }
 "smithy-http" = { version = "0.0.1", path = "../smithy-http" }
+"smithy-json" = { path = "../smithy-json" }
 "smithy-xml" = { path = "../smithy-xml" }
 "fastrand" = "1"
 

rust-runtime/smithy-json/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "smithy-json"
+version = "0.1.0"
+authors = ["AWS Rust SDK Team <aws-sdk-rust@amazon.com>", "John DiSanti <jdisanti@amazon.com>"]
+edition = "2018"
+
+[dependencies]
+itoa = "0.4"
+ryu = "1.0"
+smithy-types = { path = "../smithy-types" }
+
+[dev-dependencies]
+proptest = "1"
+serde_json = "1.0"

rust-runtime/smithy-json/src/escape.rs

@@ -0,0 +1,68 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+use std::borrow::Cow;
+
+const ESCAPES: &[char] = &['"', '\\', '\u{08}', '\u{0C}', '\n', '\r', '\t'];
+
+/// Escapes a string for embedding in a JSON string value.
+pub fn escape_string(value: &str) -> Cow<str> {
+ if !value.contains(ESCAPES) {
+ return Cow::Borrowed(value);
+ }
+
+ let mut escaped = String::new();
+ let (mut last, end) = (0, value.len());
+ for (index, chr) in value
+ .char_indices()
+ .filter(|(_index, chr)| ESCAPES.contains(chr))
+ {
+ escaped.push_str(&value[last..index]);
+ escaped.push_str(match chr {
+ '"' => "\\\"",
+ '\\' => "\\\\",
+ '\u{08}' => "\\b",
+ '\u{0C}' => "\\f",
+ '\n' => "\\n",
+ '\r' => "\\r",
+ '\t' => "\\t",
+ _ => unreachable!(),
+ });
+ last = index + 1;
+ }
+ escaped.push_str(&value[last..end]);
+ Cow::Owned(escaped)
+}
+
+#[cfg(test)]
+mod test {
+ use super::escape_string;
+
+ #[test]
+ fn escape() {
+ assert_eq!("", escape_string("").as_ref());
+ assert_eq!("foo", escape_string("foo").as_ref());
+ assert_eq!("foo\\r\\n", escape_string("foo\r\n").as_ref());
+ assert_eq!("foo\\r\\nbar", escape_string("foo\r\nbar").as_ref());
+ assert_eq!(r#"foo\\bar"#, escape_string(r#"foo\bar"#).as_ref());
+ assert_eq!(r#"\\foobar"#, escape_string(r#"\foobar"#).as_ref());
+ assert_eq!(
+ r#"\bf\fo\to\r\n"#,
+ escape_string("\u{08}f\u{0C}o\to\r\n").as_ref()
+ );
+ assert_eq!("\\\"test\\\"", escape_string("\"test\"").as_ref());
+ }
+
+ use proptest::proptest;
+ proptest! {
+ #[test]
+ fn matches_serde_json(s: String) {
+ assert_eq!(
+ serde_json::to_string(&s).unwrap(),
+ format!(r#""{}""#, escape_string(&s))
+ )
+ }
+ }
+}

rust-runtime/smithy-json/src/lib.rs

@@ -0,0 +1,9 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+//! JSON Abstractions for Smithy
+
+mod escape;
+pub mod serialize;