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"
@@ -42,6 +43,8 @@ crate-type = ["lib", "staticlib"]
 [dev-dependencies]
 regex = { workspace = true }
 toml = { workspace = true }
+tree-sitter = { workspace = true }
+tree-sitter-c = { workspace = true }
 
 [package.metadata.capi.header]
 name = "rustls"

librustls/Cargo.toml

@@ -3,6 +3,22 @@ language = "C"
 
 usize_is_size_t = true
 
+# 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))
+"""
+
 [enum]
 prefix_with_name = true
 rename_variants = "ScreamingSnakeCase"

librustls/cbindgen.toml

@@ -7,6 +7,19 @@
 #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))
+
+
 /**
  * Describes which sort of handshake happened.
  */

librustls/src/rustls.h

@@ -1,9 +1,11 @@
 #![cfg(not(feature = "capi"))]
 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};
 
 use rustls_ffi::rustls_version;
 
@@ -12,8 +14,10 @@ use rustls_ffi::rustls_version;
 /// In particular this ensures that the Rustls version reported in the rustls-ffi version string
 /// matches the version of the Rustls dependency that rustls-ffi was built with.
 ///
+/// It also ensures that the correct version parts defines are in src/rustls.h
+///
 /// If this test starts to fail, you probably forgot to update `RUSTLS_CRATE_VERSION` in
-/// `build.rs`.
+/// `build.rs`, or forgot to update cbindgen.toml with new version parts (or run cbindgen again).
 #[cfg_attr(miri, ignore)] // Requires file I/O
 #[test]
 fn rustls_version_match() {
@@ -71,4 +75,45 @@ fn rustls_version_match() {
             rustls_crypto_provider,
         ]
     );
+    let version_in_header = version_in_header();
+    assert_eq!(crate_version, version_in_header, "Version in header (.h file) doesn't match version Cargo.toml");
+}
+
+#[cfg_attr(miri, ignore)] // Requires file I/O
+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("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 root_node = tree.root_node();
+    let query = r#"( preproc_def name: (identifier) @define.name )"#;
+    let query = Query::new(&language.into(), query).unwrap();
+    let mut cursor = QueryCursor::new();
+    let matches = cursor.matches(&query, 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 parent = preproc.parent().unwrap();
+            if let Some(value_node) = parent.child_by_field_name("value") {
+                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; }
+                    _ => (),
+                }
+            }
+        }
+    }
+    return format!("{0}.{1}.{2}", version_parts[0], version_parts[1], version_parts[2]);
 }