cbindgen: Add version defines

This will allow users to check the version of rustls-ffi without
resorting to checking if functions are defined.

Also add make rustls_version_match verify that defines are the correct.

In addition to RUSTLS_VERSION_{MAJOR,MINOR,PATCH}, also define
RUSTLS_VERSION_NUMBER, which includes each version part in it, bit shifted to the
left. This is inspired by openssl[0], c-ares[1]. There are other options for
this, for example zstd multiplies each part by a power of 100[2].

We might want to also have the entire version string here, which could
help tools that need to parse the header file itself.

[0] https://github.com/openssl/openssl/blob/cdd01b5e0734b0324251b32a8edd97f42ba90429/include/openssl/opensslv.h.in#L92-L102
[1] https://github.com/c-ares/c-ares/blob/42ddbc14ec008e738fa44aa2c16e74cad93742c2/include/ares_version.h#L43-L45
[2] https://github.com/facebook/zstd/blob/3c3b8274c517727952927c705940eb90c10c736f/lib/zstd.h#L115

Fixes #557

Author: yedayak

Cargo.lock

@@ -1,5 +1,6 @@
 [package]
 name = "rustls-ffi"
+# Keep in sync with defines in cbindgen.toml
 version = "0.15.0"
 license = "Apache-2.0 OR ISC OR MIT"
 readme = "../README-crates.io.md"

librustls/Cargo.toml

@@ -1,6 +1,20 @@
 include_guard = "RUSTLS_H"
 language = "C"
+# Keep in sync with "package.version" in Cargo.toml
 after_includes = """
+
+#define RUSTLS_VERSION_MAJOR 0
+#define RUSTLS_VERSION_MINOR 15
+#define RUSTLS_VERSION_PATCH 0
+
+/**
+ * This gives each version part 8 bits, and leaves the 8 least significant bits
+ * empty for future additions, for example pre-release versions.
+ */
+#define RUSTLS_VERSION_NUMBER ((RUSTLS_VERSION_MAJOR << 24)   \\
+                               |(RUSTLS_VERSION_MINOR << 16)  \\
+                               |(RUSTLS_VERSION_MINOR << 8))
+
 #if defined(__clang__) || defined(__GNUC__)
 # define DEPRECATED_FUNC(why) __attribute__((deprecated(why)))
 #elif defined(_MSC_VER)

librustls/cbindgen.toml

@@ -6,6 +6,19 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdlib.h>
+
+#define RUSTLS_VERSION_MAJOR 0
+#define RUSTLS_VERSION_MINOR 15
+#define RUSTLS_VERSION_PATCH 0
+
+/**
+ * This gives each version part 8 bits, and leaves the 8 least significant bits
+ * empty for future additions, for example pre-release versions.
+ */
+#define RUSTLS_VERSION_NUMBER ((RUSTLS_VERSION_MAJOR << 24)   \
+                               |(RUSTLS_VERSION_MINOR << 16)  \
+                               |(RUSTLS_VERSION_MINOR << 8))
+
 #if defined(__clang__) || defined(__GNUC__)
 # define DEPRECATED_FUNC(why) __attribute__((deprecated(why)))
 #elif defined(_MSC_VER)

librustls/src/rustls.h

@@ -6,8 +6,10 @@ publish = false
 
 [dependencies]
 rustls = { workspace = true }
+rustls-ffi = { path = "../librustls" }
 hickory-resolver = { workspace = true }
 tokio = { workspace = true }
+toml = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 tree-sitter = { workspace = true }

tools/Cargo.toml

@@ -0,0 +1,91 @@
+use std::fs::File;
+use std::fs::read_to_string;
+use std::io::Read;
+use std::path::PathBuf;
+
+use toml::Table;
+use tree_sitter::{Parser, Query, QueryCursor};
+
+/// Ensure that the correct version part defines are in src/rustls.h
+///
+/// If this test starts to fail, you probably forgot to update cbindgen.toml with new version
+/// parts, or need to rerun cbindgen after updating it.
+///
+/// This test is in the tools crate because it requires an msrv of 1.76 and the librustls crate
+/// currently has an msrv of 1.73.
+#[test]
+fn rustls_header_versions_match() {
+    // Parse Cargo.toml as a generic TOML Table.
+    let mut metadata_file =
+        File::open(PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../librustls/Cargo.toml"))
+            .expect("failed to open Cargo.toml");
+    let mut metadata_content = String::new();
+    metadata_file
+        .read_to_string(&mut metadata_content)
+        .expect("failed to read Cargo.toml");
+    let metadata = metadata_content.parse::<Table>().unwrap();
+
+    // Find the crate version specified in Cargo.toml
+    let package_metadata = metadata["package"]
+        .as_table()
+        .expect("missing package metadata");
+    let crate_version = package_metadata["version"]
+        .as_str()
+        .expect("missing crate version");
+
+    let version_in_header = version_in_header();
+    assert_eq!(
+        crate_version, version_in_header,
+        "Version in header (.h file) doesn't match version in Cargo.toml"
+    );
+}
+
+fn version_in_header() -> String {
+    // Create a C parser.
+    let mut parser = Parser::new();
+    let language = tree_sitter_c::LANGUAGE;
+    parser.set_language(&language.into()).unwrap();
+
+    // Parse the .h into an AST.
+    let header_file =
+        read_to_string("../librustls/src/rustls.h").expect("Couldn't read header file");
+
+    let header_file_bytes = header_file.as_bytes();
+    let tree = parser
+        .parse(&header_file, None)
+        .ok_or("no tree parsed from input")
+        .unwrap();
+    let query = r#"
+        (preproc_def name: (identifier) @define.name
+            (#match? @define.name "^RUSTLS_VERSION_[MAJOR|MINOR|PATCH]")
+        )"#;
+    let query = Query::new(&language.into(), query).unwrap();
+    let mut cursor = QueryCursor::new();
+    let matches = cursor.matches(&query, tree.root_node(), header_file_bytes);
+    let mut version_parts: [&str; 3] = Default::default();
+    for query_match in matches {
+        for preproc in query_match.nodes_for_capture_index(0) {
+            let Some(value_node) = preproc.parent().unwrap().child_by_field_name("value") else {
+                continue;
+            };
+            let key = preproc.utf8_text(header_file_bytes).unwrap();
+            let value = value_node.utf8_text(header_file_bytes).unwrap();
+            match key {
+                "RUSTLS_VERSION_MAJOR" => {
+                    version_parts[0] = value;
+                }
+                "RUSTLS_VERSION_MINOR" => {
+                    version_parts[1] = value;
+                }
+                "RUSTLS_VERSION_PATCH" => {
+                    version_parts[2] = value;
+                }
+                _ => (),
+            }
+        }
+    }
+    format!(
+        "{0}.{1}.{2}",
+        version_parts[0], version_parts[1], version_parts[2]
+    )
+}