some more structuring. added map function to handle results more nicely.

src/ffi.rs

+extern crate libc;
+use self::libc::{c_int, c_void, size_t};
+use std::io::{IoResult, IoError};
+use std::c_vec::CVec;
+use std::c_str::CString;
+
+#[repr(C)]
+pub struct RocksdbOptions(pub *const c_void);
+#[repr(C)]
+pub struct RocksdbInstance(pub *const c_void);
+#[repr(C)]
+pub struct RocksdbWriteOptions(pub *const c_void);
+#[repr(C)]
+pub struct RocksdbReadOptions(pub *const c_void);
+#[repr(C)]
+pub struct RocksdbCompactionFilter(pub *const c_void);
+#[repr(C)]
+pub struct RocksdbMergeOperator(pub *const c_void);
+#[repr(C)]
+pub struct RocksdbFilterPolicy(pub *const c_void);
+
+#[allow(dead_code)]
+#[repr(C)]
+enum RocksdbCompressionType {
+  RocksdbNoCompression     = 0,
+  RocksdbSnappyCompression = 1,
+  RocksdbZlibCompression   = 2,
+  RocksdbBz2Compression    = 3,
+  RocksdbLz4Compression    = 4,
+  RocksdbLz4hcCompression  = 5
+}
+
+#[allow(dead_code)]
+#[repr(C)]
+enum RocksdbCompactionStyle {
+  RocksdbLevelCompaction     = 0,
+  RocksdbUniversalCompaction = 1,
+  RocksdbFifoCompaction      = 2
+}
+
+#[allow(dead_code)]
+#[repr(C)]
+enum RocksdbUniversalCompactionStyle {
+  rocksdb_similar_size_compaction_stop_style = 0,
+  rocksdb_total_size_compaction_stop_style   = 1
+}
+
+#[allow(dead_code)]
+#[link(name = "rocksdb")]
+extern {
+    pub fn rocksdb_options_create() -> RocksdbOptions;
+    pub fn rocksdb_options_increase_parallelism(
+        options: RocksdbOptions, threads: c_int);
+    pub fn rocksdb_options_optimize_level_style_compaction(
+        options: RocksdbOptions, memtable_memory_budget: c_int);
+    pub fn rocksdb_options_set_create_if_missing(
+        options: RocksdbOptions, v: c_int);
+    pub fn rocksdb_options_set_max_open_files(
+        options: RocksdbOptions, files: c_int);
+    pub fn rocksdb_options_set_use_fsync(
+        options: RocksdbOptions, v: c_int);
+    pub fn rocksdb_options_set_bytes_per_sync(
+        options: RocksdbOptions, bytes: u64);
+    pub fn rocksdb_options_set_disable_data_sync(
+        options: RocksdbOptions, v: c_int);
+    pub fn rocksdb_options_optimize_for_point_lookup(
+        options: RocksdbOptions, block_cache_size_mb: u64);
+    pub fn rocksdb_options_set_table_cache_numshardbits(
+        options: RocksdbOptions, bits: u64);
+    pub fn rocksdb_options_set_max_write_buffer_number(
+        options: RocksdbOptions, bufno: c_int);
+    pub fn rocksdb_options_set_min_write_buffer_number_to_merge(
+        options: RocksdbOptions, bufno: c_int);
+    pub fn rocksdb_options_set_level0_file_num_compaction_trigger(
+        options: RocksdbOptions, no: c_int);
+    pub fn rocksdb_options_set_level0_slowdown_writes_trigger(
+        options: RocksdbOptions, no: c_int);
+    pub fn rocksdb_options_set_level0_stop_writes_trigger(
+        options: RocksdbOptions, no: c_int);
+    pub fn rocksdb_options_set_write_buffer_size(
+        options: RocksdbOptions, bytes: u64);
+    pub fn rocksdb_options_set_target_file_size_base(
+        options: RocksdbOptions, bytes: u64);
+    pub fn rocksdb_options_set_target_file_size_multiplier(
+        options: RocksdbOptions, mul: c_int);
+    pub fn rocksdb_options_set_max_log_file_size(
+        options: RocksdbOptions, bytes: u64);
+    pub fn rocksdb_options_set_max_manifest_file_size(
+        options: RocksdbOptions, bytes: u64);
+    pub fn rocksdb_options_set_hash_skip_list_rep(
+        options: RocksdbOptions, bytes: u64, a1: i32, a2: i32);
+    pub fn rocksdb_options_set_compaction_style(
+        options: RocksdbOptions, cs: RocksdbCompactionStyle);
+    pub fn rocksdb_options_set_compression(
+        options: RocksdbOptions, compression_style_no: c_int);
+    pub fn rocksdb_options_set_max_background_compactions(
+        options: RocksdbOptions, max_bg_compactions: c_int);
+    pub fn rocksdb_options_set_max_background_flushes(
+        options: RocksdbOptions, max_bg_flushes: c_int);
+    pub fn rocksdb_options_set_filter_deletes(
+        options: RocksdbOptions, v: u8);
+    //pub fn rocksdb_compactionfilter_create() -> RocksdbCompactionFilter;
+    //pub fn rocksdb_mergeoperator_create() -> RocksdbMergeOperator;
+    pub fn rocksdb_filterpolicy_create_bloom(
+        bits_per_key: c_int) -> RocksdbFilterPolicy;
+    pub fn rocksdb_open(options: RocksdbOptions,
+        path: *const i8, err: *mut i8) -> RocksdbInstance;
+    pub fn rocksdb_writeoptions_create() -> RocksdbWriteOptions;
+    pub fn rocksdb_put(db: RocksdbInstance, writeopts: RocksdbWriteOptions,
+        k: *const u8, kLen: size_t, v: *const u8,
+        vLen: size_t, err: *mut i8);
+    pub fn rocksdb_readoptions_create() -> RocksdbReadOptions;
+    pub fn rocksdb_get(db: RocksdbInstance, readopts: RocksdbReadOptions,
+        k: *const u8, kLen: size_t,
+        valLen: *const size_t, err: *mut i8) -> *mut u8;
+    pub fn rocksdb_close(db: RocksdbInstance);
+}
+
+#[test]
+fn internal() {
+    unsafe {
+        let opts = rocksdb_options_create();
+        let RocksdbOptions(opt_ptr) = opts;
+        assert!(opt_ptr.is_not_null());
+        
+        rocksdb_options_increase_parallelism(opts, 0);
+        rocksdb_options_optimize_level_style_compaction(opts, 0);
+        rocksdb_options_set_create_if_missing(opts, 1);
+
+        let rustpath = "datadir";
+        let cpath = rustpath.to_c_str();
+        let cpath_ptr = cpath.as_ptr();
+        
+        //TODO this will SIGSEGV
+        let err = 0 as *mut i8;
+        let db = rocksdb_open(opts, cpath_ptr, err); 
+        assert!(err.is_null());
+        libc::free(err as *mut c_void);
+
+        let writeopts = rocksdb_writeoptions_create();
+        let RocksdbWriteOptions(write_opt_ptr) = writeopts;
+        assert!(write_opt_ptr.is_not_null());
+
+        let key = b"name\x00";
+        let val = b"spacejam\x00";
+
+        rocksdb_put(db, writeopts, key.as_ptr(), 4, val.as_ptr(), 8, err);
+        assert!(err.is_null());
+        libc::free(err as *mut c_void);
+
+        let readopts = rocksdb_readoptions_create();
+        let RocksdbReadOptions(read_opts_ptr) = readopts;
+        assert!(read_opts_ptr.is_not_null());
+        libc::free(err as *mut c_void);
+
+        let mut val_len: size_t = 0;
+        let val_len_ptr = &val_len as *const size_t;
+        rocksdb_get(db, readopts, key.as_ptr(), 4, val_len_ptr, err);
+        assert!(err.is_null());
+        libc::free(err as *mut c_void);
+        rocksdb_close(db);
+    }
+}

src/lib.rs

 #![crate_id = "rocksdb"]
 #![crate_type = "lib"]
+#![feature(globs)]
 
 pub use rocksdb::{
     open,
     Rocksdb,
+    RocksdbResult,
 };
 pub mod rocksdb;
+mod ffi;

src/main.rs

@@ -4,7 +4,10 @@ use rocksdb::open;
 use test::Bencher;
 
 fn main() {
-    println!("test");
+    let db = open("testdb".to_string(), true).unwrap();
+    db.put(b"hey", b"v1111");
+    db.get(b"hey").map(|v| { println!("value: {}", v.as_slice()); });
+    db.close();
 }
 
 #[bench]

src/rocksdb.rs

 extern crate libc;
 use self::libc::{c_int, c_void, size_t};
-use std::io::{IoResult, IoError, BufferedStream};
+use std::io::{IoResult, IoError};
 use std::c_vec::CVec;
+use std::c_str::CString;
 
-#[repr(C)]
-struct RocksdbOptions(*const c_void);
-#[repr(C)]
-struct RocksdbInstance(*const c_void);
-#[repr(C)]
-struct RocksdbWriteOptions(*const c_void);
-#[repr(C)]
-struct RocksdbReadOptions(*const c_void);
-#[repr(C)]
-struct RocksdbCompactionFilter(*const c_void);
-#[repr(C)]
-struct RocksdbMergeOperator(*const c_void);
-#[repr(C)]
-struct RocksdbFilterPolicy(*const c_void);
+use ffi;
 
-#[repr(C)]
-enum RocksdbCompressionType {
-  RocksdbNoCompression     = 0,
-  RocksdbSnappyCompression = 1,
-  RocksdbZlibCompression   = 2,
-  RocksdbBz2Compression    = 3,
-  RocksdbLz4Compression    = 4,
-  RocksdbLz4hcCompression  = 5
+// TODO learn more about lifetimes and determine if it's appropriate to keep
+// inner on the stack, instead.
+pub struct RocksdbVector {
+    inner: Box<CVec<u8>>,
 }
 
-#[repr(C)]
-enum RocksdbCompactionStyle {
-  RocksdbLevelCompaction     = 0,
-  RocksdbUniversalCompaction = 1,
-  RocksdbFifoCompaction      = 2
+impl RocksdbVector {
+    pub fn from_c(val: *mut u8, val_len: size_t) -> RocksdbVector {
+        unsafe {
+            RocksdbVector{
+                inner:
+                    box CVec::new_with_dtor(val, val_len as uint,
+                        proc(){
+                            libc::free(val as *mut c_void);
+                        })}
+        }
+    }
+
+    pub fn as_slice(&self) -> &[u8] {
+        self.inner.as_slice()
+    }
 }
 
-#[repr(C)]
-enum RocksdbUniversalCompactionStyle {
-  rocksdb_similar_size_compaction_stop_style = 0,
-  rocksdb_total_size_compaction_stop_style   = 1
+
+#[deriving(Clone, PartialEq, PartialOrd, Eq, Ord, Show)]
+pub enum RocksdbResult<T, E> {
+    Some(T),
+    None,
+    Error(E),
 }
 
+impl <T,E> RocksdbResult<T,E> {
+    #[unstable = "waiting for unboxed closures"]
+    pub fn map<U>(self, f: |T| -> U) -> RocksdbResult<U,E> {
+        match self {
+            RocksdbResult::Some(x) => RocksdbResult::Some(f(x)),
+            RocksdbResult::None => RocksdbResult::None,
+            RocksdbResult::Error(e) => RocksdbResult::Error(e),
+        }
+    }
 
-#[link(name = "rocksdb")]
-extern {
-    fn rocksdb_options_create() -> RocksdbOptions;
-    fn rocksdb_options_increase_parallelism(
-        options: RocksdbOptions, threads: c_int);
-    fn rocksdb_options_optimize_level_style_compaction(
-        options: RocksdbOptions, memtable_memory_budget: c_int);
-    fn rocksdb_options_set_create_if_missing(
-        options: RocksdbOptions, v: c_int);
-    fn rocksdb_options_set_max_open_files(
-        options: RocksdbOptions, files: c_int);
-    fn rocksdb_options_set_use_fsync(
-        options: RocksdbOptions, v: c_int);
-    fn rocksdb_options_set_bytes_per_sync(
-        options: RocksdbOptions, bytes: u64);
-    fn rocksdb_options_set_disable_data_sync(
-        options: RocksdbOptions, v: c_int);
-    fn rocksdb_options_optimize_for_point_lookup(
-        options: RocksdbOptions, block_cache_size_mb: u64);
-    fn rocksdb_options_set_table_cache_numshardbits(
-        options: RocksdbOptions, bits: u64);
-    fn rocksdb_options_set_max_write_buffer_number(
-        options: RocksdbOptions, bufno: c_int);
-    fn rocksdb_options_set_min_write_buffer_number_to_merge(
-        options: RocksdbOptions, bufno: c_int);
-    fn rocksdb_options_set_level0_file_num_compaction_trigger(
-        options: RocksdbOptions, no: c_int);
-    fn rocksdb_options_set_level0_slowdown_writes_trigger(
-        options: RocksdbOptions, no: c_int);
-    fn rocksdb_options_set_level0_stop_writes_trigger(
-        options: RocksdbOptions, no: c_int);
-    fn rocksdb_options_set_write_buffer_size(
-        options: RocksdbOptions, bytes: u64);
-    fn rocksdb_options_set_target_file_size_base(
-        options: RocksdbOptions, bytes: u64);
-    fn rocksdb_options_set_target_file_size_multiplier(
-        options: RocksdbOptions, mul: c_int);
-    fn rocksdb_options_set_max_log_file_size(
-        options: RocksdbOptions, bytes: u64);
-    fn rocksdb_options_set_max_manifest_file_size(
-        options: RocksdbOptions, bytes: u64);
-    fn rocksdb_options_set_hash_skip_list_rep(
-        options: RocksdbOptions, bytes: u64, a1: i32, a2: i32);
-    fn rocksdb_options_set_compaction_style(
-        options: RocksdbOptions, cs: RocksdbCompactionStyle);
-    fn rocksdb_options_set_compression(
-        options: RocksdbOptions, compression_style_no: c_int);
-    fn rocksdb_options_set_max_background_compactions(
-        options: RocksdbOptions, max_bg_compactions: c_int);
-    fn rocksdb_options_set_max_background_flushes(
-        options: RocksdbOptions, max_bg_flushes: c_int);
-    fn rocksdb_options_set_filter_deletes(
-        options: RocksdbOptions, v: u8);
-    //fn rocksdb_compactionfilter_create() -> RocksdbCompactionFilter;
-    //fn rocksdb_mergeoperator_create() -> RocksdbMergeOperator;
-    fn rocksdb_filterpolicy_create_bloom(
-        bits_per_key: c_int) -> RocksdbFilterPolicy;
-    fn rocksdb_open(options: RocksdbOptions,
-        path: *const i8, err: *mut i8) -> RocksdbInstance;
-    fn rocksdb_writeoptions_create() -> RocksdbWriteOptions;
-    fn rocksdb_put(db: RocksdbInstance, writeopts: RocksdbWriteOptions,
-        k: *const u8, kLen: size_t, v: *const u8,
-        vLen: size_t, err: *mut i8);
-    fn rocksdb_readoptions_create() -> RocksdbReadOptions;
-    fn rocksdb_get(db: RocksdbInstance, readopts: RocksdbReadOptions,
-        k: *const u8, kLen: size_t,
-        valLen: *const size_t, err: *mut i8) -> *mut u8;
-    fn rocksdb_close(db: RocksdbInstance);
+    pub fn is_some(self) -> bool {
+        match self {
+            RocksdbResult::Some(T) => true,
+            RocksdbResult::None => false,
+            RocksdbResult::Error(E) => false,
+        }
+    }
+    pub fn is_none(self) -> bool {
+        match self {
+            RocksdbResult::Some(T) => false,
+            RocksdbResult::None => true,
+            RocksdbResult::Error(E) => false,
+        }
+    }
+    pub fn is_error(self) -> bool {
+        match self {
+            RocksdbResult::Some(T) => false,
+            RocksdbResult::None => false,
+            RocksdbResult::Error(E) => true,
+        }
+    }
 }
 
 pub struct Rocksdb {
-    inner: RocksdbInstance,
+    inner: ffi::RocksdbInstance,
     path: String,
 }
 
 impl Rocksdb {
     pub fn put(&self, key: &[u8], value: &[u8]) -> IoResult<bool> {
         unsafe {   
-            let writeopts = rocksdb_writeoptions_create();
+            let writeopts = ffi::rocksdb_writeoptions_create();
             let err = 0 as *mut i8;
-            rocksdb_put(self.inner, writeopts, key.as_ptr(),
+            ffi::rocksdb_put(self.inner, writeopts, key.as_ptr(),
                         key.len() as size_t, value.as_ptr(),
                         value.len() as size_t, err);
             if err.is_not_null() {
@@ -134,59 +92,70 @@ impl Rocksdb {
         }
     }
 
-    pub fn get(&self, key: &[u8]) -> IoResult<CVec<u8>> {
+    pub fn get(&self, key: &[u8]) -> RocksdbResult<RocksdbVector, String> {
         unsafe {
-            let readopts = rocksdb_readoptions_create();
-            let RocksdbReadOptions(read_opts_ptr) = readopts;
+            let readopts = ffi::rocksdb_readoptions_create();
+            let ffi::RocksdbReadOptions(read_opts_ptr) = readopts;
             if read_opts_ptr.is_null() {
-                return Err(IoError::last_error());
+                return RocksdbResult::Error("Unable to create rocksdb read \
+                    options.  This is a fairly trivial call, and its failure \
+                    may be indicative of a mis-compiled or mis-loaded rocksdb \
+                    library.".to_string());
             }
 
             let val_len: size_t = 0;
             let val_len_ptr = &val_len as *const size_t;
             let err = 0 as *mut i8;
-            let val = rocksdb_get(self.inner, readopts, key.as_ptr(),
+            let val = ffi::rocksdb_get(self.inner, readopts, key.as_ptr(),
                                   key.len() as size_t, val_len_ptr, err);
             if err.is_not_null() {
-                libc::free(err as *mut c_void);
-                return Err(IoError::last_error());
+                let cs = CString::new(err as *const i8, true);
+                match cs.as_str() {
+                    Some(error_string) =>
+                        return RocksdbResult::Error(error_string.to_string()),
+                    None =>
+                        return RocksdbResult::Error("Unable to get value from \
+                            rocksdb. (non-utf8 error received from underlying \
+                            library)".to_string()),
+                }
+            }
+            match val.is_null() {
+                true =>  RocksdbResult::None,
+                false => {
+                    RocksdbResult::Some(RocksdbVector::from_c(val, val_len))
+                }
             }
-            libc::free(err as *mut c_void);
-            return Ok(CVec::new_with_dtor(val, val_len as uint,
-                        proc(){
-                            libc::free(val as *mut c_void);
-                        }))
         }
     }
 
     pub fn close(&self) {
-        unsafe { rocksdb_close(self.inner); }
+        unsafe { ffi::rocksdb_close(self.inner); }
     }
 
 }
 
 pub fn open(path: String, create_if_missing: bool) -> Result<Rocksdb, String> {
     unsafe {
-        let opts = rocksdb_options_create();
-        let RocksdbOptions(opt_ptr) = opts;
+        let opts = ffi::rocksdb_options_create();
+        let ffi::RocksdbOptions(opt_ptr) = opts;
         if opt_ptr.is_null() {
             return Err("Could not create options".to_string());
         }
         
-        rocksdb_options_increase_parallelism(opts, 0);
-        rocksdb_options_optimize_level_style_compaction(opts, 0);
+        ffi::rocksdb_options_increase_parallelism(opts, 0);
+        ffi::rocksdb_options_optimize_level_style_compaction(opts, 0);
 
         match create_if_missing {
-            true => rocksdb_options_set_create_if_missing(opts, 1),
-            false => rocksdb_options_set_create_if_missing(opts, 0),
+            true => ffi::rocksdb_options_set_create_if_missing(opts, 1),
+            false => ffi::rocksdb_options_set_create_if_missing(opts, 0),
         }
 
         let cpath = path.to_c_str();
         let cpath_ptr = cpath.as_ptr();
         
         let err = 0 as *mut i8;
-        let db = rocksdb_open(opts, cpath_ptr, err); 
-        let RocksdbInstance(db_ptr) = db;
+        let db = ffi::rocksdb_open(opts, cpath_ptr, err); 
+        let ffi::RocksdbInstance(db_ptr) = db;
         if err.is_not_null() {
             libc::free(err as *mut c_void);
             return Err("Could not initialize database.".to_string());
@@ -199,58 +168,12 @@ pub fn open(path: String, create_if_missing: bool) -> Result<Rocksdb, String> {
     }
 }
 
-#[test]
-fn internal() {
-    unsafe {
-        let opts = rocksdb_options_create();
-        let RocksdbOptions(opt_ptr) = opts;
-        assert!(opt_ptr.is_not_null());
-        
-        rocksdb_options_increase_parallelism(opts, 0);
-        rocksdb_options_optimize_level_style_compaction(opts, 0);
-        rocksdb_options_set_create_if_missing(opts, 1);
-
-        let rustpath = "datadir";
-        let cpath = rustpath.to_c_str();
-        let cpath_ptr = cpath.as_ptr();
-        
-        //TODO this will SIGSEGV
-        let err = 0 as *mut i8;
-        let db = rocksdb_open(opts, cpath_ptr, err); 
-        assert!(err.is_null());
-        libc::free(err as *mut c_void);
-
-        let writeopts = rocksdb_writeoptions_create();
-        let RocksdbWriteOptions(write_opt_ptr) = writeopts;
-        assert!(write_opt_ptr.is_not_null());
-
-        let key = b"name\x00";
-        let val = b"spacejam\x00";
-
-        rocksdb_put(db, writeopts, key.as_ptr(), 4, val.as_ptr(), 8, err);
-        assert!(err.is_null());
-        libc::free(err as *mut c_void);
-
-        let readopts = rocksdb_readoptions_create();
-        let RocksdbReadOptions(read_opts_ptr) = readopts;
-        assert!(read_opts_ptr.is_not_null());
-        libc::free(err as *mut c_void);
-
-        let mut val_len: size_t = 0;
-        let val_len_ptr = &val_len as *const size_t;
-        rocksdb_get(db, readopts, key.as_ptr(), 4, val_len_ptr, err);
-        assert!(err.is_null());
-        libc::free(err as *mut c_void);
-        rocksdb_close(db);
-    }
-}
-
 #[test]
 fn external() {
     let db = open("testdb".to_string(), true).unwrap();
     db.put(b"k1", b"v1111");
-    let r = db.get(b"k1").unwrap();
-    assert!(r.len() == 5);
-    let v = r.get(0).unwrap();
+    let r: RocksdbResult<RocksdbVector, String> = db.get(b"k1");
+    //assert!(r.is_some());
+    r.map(|v| { assert!(v.as_slice().len() == 5); } );
     db.close();
 }