main: Write YAML to standard output

Create an adapter from `std::fmt::Write` to `std::io::Write` based on
the following idea in the standard library:

https://github.com/rust-lang/rust/blob/master/library/std/src/io/mod.rs#L1634-L1652

Since `yaml_rust::YamlEmitter::new()` requires a `std::fmt::Write`,
adapt standard output so the emitter can write to it.

3 files changed, 25 insertions, 3 deletions

diff --git a/src/main.rs b/src/main.rs
index 7f372ea..2ac689c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -94,9 +94,10 @@ fn main() {
                 ).unwrap(),
             };
 
-            let mut emitter = yaml_rust::YamlEmitter::new(
-                &mut std::io::stdout().lock(),
-            );
+            let stdout = std::io::stdout();
+            let mut stdout_handle = stdout.lock();
+            let mut buffer = yaqlite::yaml::IoAdapter::new(&mut stdout_handle);
+            let mut emitter = yaml_rust::YamlEmitter::new(&mut buffer);
             emitter.dump(&yaml_data).unwrap();
 
             dbconn.close().unwrap();
diff --git a/src/yaml.rs b/src/yaml.rs
index 77665b3..9b0988c 100644
--- a/src/yaml.rs
+++ b/src/yaml.rs
@@ -5,9 +5,12 @@ use std::collections::HashMap;
 
 
 mod sql;
+mod write;
 
 pub(crate) use sql::*;
 
+pub use write::*;
+
 
 // TODO: Separate functions to get a list of YAML hashes, and insert hashes into
 // the database.
diff --git a/src/yaml/write.rs b/src/yaml/write.rs
new file mode 100644
index 0000000..a1e52a5
--- /dev/null
+++ b/src/yaml/write.rs
@@ -0,0 +1,18 @@
+pub struct IoAdapter<'a, T: std::io::Write> {
+    inner: &'a mut T,
+}
+
+impl<'a, T: std::io::Write> IoAdapter<'a, T> {
+    pub fn new(writer: &'a mut T) -> Self {
+        IoAdapter { inner: writer }
+    }
+}
+
+impl<T: std::io::Write> std::fmt::Write for IoAdapter<'_, T> {
+    fn write_str(&mut self, s: &str) -> std::fmt::Result {
+        match self.inner.write_all(s.as_bytes()) {
+            Ok(()) => Ok(()),
+            Err(_) => Err(std::fmt::Error),
+        }
+    }
+}