From 70f6125a3d0fb42e89d4fac0a8b933d06d8d902e Mon Sep 17 00:00:00 2001
From: Nikhil Benesch <nikhil.benesch@gmail.com>
Date: Tue, 23 Apr 2019 15:27:17 -0400
Subject: [PATCH] Add an ErrBuf helper to manage APIs with error strings

---
 src/client.rs |  9 ++++-----
 src/config.rs | 14 +++++---------
 src/util.rs   | 30 ++++++++++++++++++++++++++++++
 3 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/src/client.rs b/src/client.rs
index 030513648..ac465930a 100644
--- a/src/client.rs
+++ b/src/client.rs
@@ -18,7 +18,7 @@ use crate::error::{IsError, KafkaError, KafkaResult};
 use crate::groups::GroupList;
 use crate::metadata::Metadata;
 use crate::statistics::Statistics;
-use crate::util::{bytes_cstr_to_owned, timeout_to_ms};
+use crate::util::{ErrBuf, timeout_to_ms};
 
 /// Client-level context
 ///
@@ -116,7 +116,7 @@ impl<C: ClientContext> Client<C> {
     pub fn new(config: &ClientConfig, native_config: NativeClientConfig, rd_kafka_type: RDKafkaType,
                context: C)
             -> KafkaResult<Client<C>> {
-        let errstr = [0i8; 1024];
+        let mut err_buf = ErrBuf::new();
         let mut boxed_context = Box::new(context);
         unsafe { rdsys::rd_kafka_conf_set_opaque(native_config.ptr(), (&mut *boxed_context) as *mut C as *mut c_void) };
         unsafe { rdsys::rd_kafka_conf_set_log_cb(native_config.ptr(), Some(native_log_cb::<C>)) };
@@ -124,13 +124,12 @@ impl<C: ClientContext> Client<C> {
         unsafe { rdsys::rd_kafka_conf_set_error_cb(native_config.ptr(), Some(native_error_cb::<C>)) };
 
         let client_ptr = unsafe {
-            rdsys::rd_kafka_new(rd_kafka_type, native_config.ptr_move(), errstr.as_ptr() as *mut c_char, errstr.len())
+            rdsys::rd_kafka_new(rd_kafka_type, native_config.ptr_move(), err_buf.as_mut_ptr(), err_buf.len())
         };
         trace!("Create new librdkafka client {:p}", client_ptr);
 
         if client_ptr.is_null() {
-            let descr = unsafe { bytes_cstr_to_owned(&errstr) };
-            return Err(KafkaError::ClientCreation(descr));
+            return Err(KafkaError::ClientCreation(err_buf.to_string()));
         }
 
         unsafe { rdsys::rd_kafka_set_log_level(client_ptr, config.log_level as i32) };
diff --git a/src/config.rs b/src/config.rs
index 6ab2c0e08..83d569ce1 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -24,14 +24,11 @@ use crate::rdsys;
 
 use crate::client::ClientContext;
 use crate::error::{KafkaError, KafkaResult, IsError};
-use crate::util::bytes_cstr_to_owned;
+use crate::util::ErrBuf;
 
 use std::collections::HashMap;
 use std::ffi::CString;
 use std::mem;
-use std::os::raw::c_char;
-
-const ERR_LEN: usize = 256;
 
 
 /// The log levels supported by librdkafka.
@@ -146,17 +143,16 @@ impl ClientConfig {
     /// Returns the native rdkafka-sys configuration.
     pub fn create_native_config(&self) -> KafkaResult<NativeClientConfig> {
         let conf = unsafe { rdsys::rd_kafka_conf_new() };
-        let errstr = [0; ERR_LEN];
+        let mut err_buf = ErrBuf::new();
         for (key, value) in &self.conf_map {
             let key_c = CString::new(key.to_string())?;
             let value_c = CString::new(value.to_string())?;
             let ret = unsafe {
                 rdsys::rd_kafka_conf_set(conf, key_c.as_ptr(), value_c.as_ptr(),
-                                           errstr.as_ptr() as *mut c_char, errstr.len())
+                                         err_buf.as_mut_ptr(), err_buf.len())
             };
-            if ret.is_error() {
-                let descr = unsafe { bytes_cstr_to_owned(&errstr) };
-                return Err(KafkaError::ClientConfig(ret, descr, key.to_string(), value.to_string()));
+            if ret.is_error() {;
+                return Err(KafkaError::ClientConfig(ret, err_buf.to_string(), key.to_string(), value.to_string()));
             }
         }
         Ok(unsafe {NativeClientConfig::from_ptr(conf)})
diff --git a/src/util.rs b/src/util.rs
index f3d86203e..feb0d7c94 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -111,6 +111,36 @@ pub unsafe fn cstr_to_owned(cstr: *const i8) -> String {
     CStr::from_ptr(cstr as *const c_char).to_string_lossy().into_owned()
 }
 
+pub(crate) struct ErrBuf {
+    buf: [c_char; ErrBuf::MAX_ERR_LEN]
+}
+
+impl ErrBuf {
+    const MAX_ERR_LEN: usize = 512;
+
+    pub fn new() -> ErrBuf {
+        ErrBuf { buf: [0; ErrBuf::MAX_ERR_LEN] }
+    }
+
+    pub fn as_mut_ptr(&mut self) -> *mut i8 {
+        self.buf.as_mut_ptr()
+    }
+
+    pub fn len(&self) -> usize {
+        self.buf.len()
+    }
+
+    pub fn to_string(&self) -> String {
+        unsafe { bytes_cstr_to_owned(&self.buf) }
+    }
+}
+
+impl Default for ErrBuf {
+    fn default() -> ErrBuf {
+        ErrBuf::new()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;