Add a Credman logger

It's compile time stripped unless we enable with `--no-default-features
--features logging` during cargo build

Author: netheril96

matcher-rs/Cargo.lock

@@ -9,6 +9,12 @@ crate-type = ["cdylib", "rlib"]
 
 [dependencies]
 nanoserde = "0.1"
+log = "0.4"
+
+[features]
+default = ["static_log_off"]
+static_log_off = ["log/max_level_off"]
+logging = []
 
 [dev-dependencies]
 

matcher-rs/Cargo.toml

@@ -12,6 +12,6 @@ cargo +nightly build \
 
 # 2. Further shrink using wasm-opt (if available)
 for wasm in target/wasm32-unknown-unknown/release/*.wasm; do
-  wasm-opt -Oz --strip-debug --enable-bulk-memory --enable-sign-ext "$wasm" -o "$wasm"
+  wasm-opt -Oz --strip-debug --enable-bulk-memory --enable-sign-ext --enable-nontrapping-float-to-int "$wasm" -o "$wasm"
 done
 

matcher-rs/build.sh

@@ -1,6 +1,7 @@
 use matcher_rs::{credman::CredmanApiImpl, issuance::issuance_main};
 
 fn main() {
+    matcher_rs::logger::init();
     issuance_main(&mut CredmanApiImpl {}).unwrap();
 }
 

matcher-rs/src/bin/issuance.rs

@@ -139,4 +139,6 @@ unsafe extern "C" {
         set_id: *const c_char,
         set_index: i32,
     );
+    pub fn fd_write(fd: i32, iovs_ptr: *const c_void, iovs_len: i32, nwritten_ptr: *mut i32)
+    -> i32;
 }

matcher-rs/src/bindings.rs

@@ -2,4 +2,5 @@ pub mod bindings;
 pub mod credman;
 pub mod issuance;
 pub mod issuance_matcher;
+pub mod logger;
 pub mod openid4vci;

matcher-rs/src/lib.rs

@@ -0,0 +1,91 @@
+//! WASM Logging implementation using `fd_write`.
+//!
+//! Logging is stripped by default at compile time to minimize the WASM binary size,
+//! as the `log` crate and string formatting (fmt) significantly increase the footprint.
+//!
+//! To enable logging during development:
+//! Use `--no-default-features --features logging` when building.
+//!
+//! Example:
+//! cargo build --release --no-default-features --features logging
+
+#[cfg(feature = "logging")]
+use crate::bindings::fd_write;
+#[cfg(feature = "logging")]
+use log::{Metadata, Record};
+#[cfg(feature = "logging")]
+use std::os::raw::c_void;
+
+#[cfg(feature = "logging")]
+struct WasmLogger;
+
+#[cfg(feature = "logging")]
+#[repr(C)]
+struct Ciovec {
+    buf: *const u8,
+    buf_len: u32,
+}
+
+#[cfg(feature = "logging")]
+impl log::Log for WasmLogger {
+    fn enabled(&self, _metadata: &Metadata) -> bool {
+        true
+    }
+
+    fn log(&self, record: &Record) {
+        if self.enabled(record.metadata()) {
+            let msg = format!("{}: {}\n", record.level(), record.args());
+            let ciovec = Ciovec {
+                buf: msg.as_ptr(),
+                buf_len: msg.len() as u32,
+            };
+            let mut nwritten = 0;
+            unsafe {
+                fd_write(
+                    1, // stdout
+                    &ciovec as *const _ as *const c_void,
+                    1,
+                    &mut nwritten,
+                );
+            }
+        }
+    }
+
+    fn flush(&self) {}
+}
+
+#[cfg(feature = "logging")]
+static LOGGER: WasmLogger = WasmLogger;
+
+#[cfg(feature = "logging")]
+pub fn init() {
+    log::set_logger(&LOGGER)
+        .map(|()| log::set_max_level(log::LevelFilter::Trace))
+        .ok();
+
+    std::panic::set_hook(Box::new(|panic_info| {
+        let msg = panic_info.payload_as_str().unwrap_or("unknown");
+        let formatted = match panic_info.location() {
+            Some(loc) => format!("Panic at {}: {}\n", loc, msg),
+            None => format!("Panic: {}\n", msg),
+        };
+        let ciovec = Ciovec {
+            buf: formatted.as_ptr(),
+            buf_len: formatted.len() as u32,
+        };
+        let mut nwritten = 0;
+        unsafe {
+            fd_write(
+                1, // stdout
+                &ciovec as *const _ as *const c_void,
+                1,
+                &mut nwritten,
+            );
+        }
+    }));
+}
+
+#[cfg(not(feature = "logging"))]
+pub fn init() {
+    log::set_max_level(log::LevelFilter::Off);
+}