add bytes starts-with command (#5950)

* refactor operate, make it generic

* refactor operate, add starts with command

* add comment

* remove useless file

crates/nu-command/src/bytes/length.rs

@@ -1,3 +1,4 @@
+use super::{operate, BytesArgument};
 use nu_engine::CallExt;
 use nu_protocol::ast::Call;
 use nu_protocol::ast::CellPath;
@@ -8,6 +9,16 @@ use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShap
 #[derive(Clone)]
 pub struct BytesLen;
 
+struct Arguments {
+    column_paths: Option<Vec<CellPath>>,
+}
+
+impl BytesArgument for Arguments {
+    fn take_column_paths(&mut self) -> Option<Vec<CellPath>> {
+        self.column_paths.take()
+    }
+}
+
 impl Command for BytesLen {
     fn name(&self) -> &str {
         "bytes length"
@@ -38,7 +49,14 @@ impl Command for BytesLen {
         call: &Call,
         input: PipelineData,
     ) -> Result<PipelineData, ShellError> {
-        operate(engine_state, stack, call, input)
+        let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 1)?;
+        let column_paths = if column_paths.is_empty() {
+            None
+        } else {
+            Some(column_paths)
+        };
+        let arg = Arguments { column_paths };
+        operate(length, arg, input, call.head, engine_state.ctrlc.clone())
     }
 
     fn examples(&self) -> Vec<Example> {
@@ -60,48 +78,10 @@ impl Command for BytesLen {
     }
 }
 
-fn operate(
-    engine_state: &EngineState,
-    stack: &mut Stack,
-    call: &Call,
-    input: PipelineData,
-) -> Result<PipelineData, ShellError> {
-    let head = call.head;
-    let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 0)?;
-    if column_paths.is_empty() {
-        input.map(move |v| action(&v, head), engine_state.ctrlc.clone())
-    } else {
-        input.map(
-            move |mut v| {
-                for path in &column_paths {
-                    let r =
-                        v.update_cell_path(&path.members, Box::new(move |old| action(old, head)));
-                    if let Err(error) = r {
-                        return Value::Error { error };
-                    }
-                }
-                v
-            },
-            engine_state.ctrlc.clone(),
-        )
-    }
-}
-
-fn action(input: &Value, head: Span) -> Value {
-    match input {
-        Value::Binary { val, .. } => Value::Int {
-            val: val.len() as i64,
-            span: head,
-        },
-        other => Value::Error {
-            error: ShellError::UnsupportedInput(
-                format!(
-                    "Input's type is {}. This command only works with bytes.",
-                    other.get_type()
-                ),
-                head,
-            ),
-        },
+fn length(input: &[u8], _arg: &Arguments, span: Span) -> Value {
+    Value::Int {
+        val: input.len() as i64,
+        span,
     }
 }
 

crates/nu-command/src/bytes/mod.rs

@@ -1,3 +1,77 @@
 mod length;
+mod starts_with;
+use nu_protocol::ast::CellPath;
+use nu_protocol::{PipelineData, ShellError, Span, Value};
+use std::sync::atomic::AtomicBool;
+use std::sync::Arc;
 
 pub use length::BytesLen;
+pub use starts_with::BytesStartsWith;
+
+trait BytesArgument {
+    fn take_column_paths(&mut self) -> Option<Vec<CellPath>>;
+}
+
+/// map input pipeline data, for each elements, if it's Binary, invoke relative `cmd` with `arg`.
+fn operate<C, A>(
+    cmd: C,
+    mut arg: A,
+    input: PipelineData,
+    span: Span,
+    ctrlc: Option<Arc<AtomicBool>>,
+) -> Result<PipelineData, ShellError>
+where
+    A: BytesArgument + Send + Sync + 'static,
+    C: Fn(&[u8], &A, Span) -> Value + Send + Sync + 'static + Clone + Copy,
+{
+    match arg.take_column_paths() {
+        None => input.map(
+            move |v| match v {
+                Value::Binary {
+                    val,
+                    span: val_span,
+                } => cmd(&val, &arg, val_span),
+                other => Value::Error {
+                    error: ShellError::UnsupportedInput(
+                        format!(
+                            "Input's type is {}. This command only works with bytes.",
+                            other.get_type()
+                        ),
+                        span,
+                    ),
+                },
+            },
+            ctrlc,
+        ),
+        Some(column_paths) => {
+            let arg = Arc::new(arg);
+            input.map(
+                move |mut v| {
+                    for path in &column_paths {
+                        let opt = arg.clone();
+                        let r = v.update_cell_path(
+                            &path.members,
+                            Box::new(move |old| {
+                                match old {
+                                    Value::Binary {val, span: val_span} => cmd(val, &opt, *val_span),
+                                    other => Value::Error {
+                                    error: ShellError::UnsupportedInput(
+                                        format!(
+                                            "Input's type is {}. This command only works with bytes.",
+                                            other.get_type()
+                                        ),
+                                        span,
+                                 ),
+                            }}}),
+                        );
+                        if let Err(error) = r {
+                            return Value::Error { error };
+                        }
+                    }
+                    v
+                },
+                ctrlc,
+            )
+        }
+    }
+}

crates/nu-command/src/bytes/starts_with.rs

@@ -0,0 +1,122 @@
+use super::{operate, BytesArgument};
+use nu_engine::CallExt;
+use nu_protocol::ast::Call;
+use nu_protocol::ast::CellPath;
+use nu_protocol::engine::{Command, EngineState, Stack};
+use nu_protocol::Category;
+use nu_protocol::{Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value};
+
+struct Arguments {
+    pattern: Vec<u8>,
+    column_paths: Option<Vec<CellPath>>,
+}
+
+impl BytesArgument for Arguments {
+    fn take_column_paths(&mut self) -> Option<Vec<CellPath>> {
+        self.column_paths.take()
+    }
+}
+
+#[derive(Clone)]
+
+pub struct BytesStartsWith;
+
+impl Command for BytesStartsWith {
+    fn name(&self) -> &str {
+        "bytes starts-with"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("bytes starts-with")
+            .required("pattern", SyntaxShape::Binary, "the pattern to match")
+            .rest(
+                "rest",
+                SyntaxShape::CellPath,
+                "optionally matches prefix of text by column paths",
+            )
+            .category(Category::Bytes)
+    }
+
+    fn usage(&self) -> &str {
+        "Check if bytes starts with a pattern"
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["pattern", "match", "find", "search"]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let pattern: Vec<u8> = call.req(engine_state, stack, 0)?;
+        let column_paths: Vec<CellPath> = call.rest(engine_state, stack, 1)?;
+        let column_paths = if column_paths.is_empty() {
+            None
+        } else {
+            Some(column_paths)
+        };
+        let arg = Arguments {
+            pattern,
+            column_paths,
+        };
+        operate(
+            starts_with,
+            arg,
+            input,
+            call.head,
+            engine_state.ctrlc.clone(),
+        )
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Checks if binary starts with `0x[1F FF AA]`",
+                example: "0x[1F FF AA AA] | bytes starts-with 0x[1F FF AA]",
+                result: Some(Value::Bool {
+                    val: true,
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description: "Checks if binary starts with `0x[1F]`",
+                example: "0x[1F FF AA AA] | bytes starts-with 0x[1F]",
+                result: Some(Value::Bool {
+                    val: true,
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description: "Checks if binary starts with `0x[1F]`",
+                example: "0x[1F FF AA AA] | bytes starts-with 0x[11]",
+                result: Some(Value::Bool {
+                    val: false,
+                    span: Span::test_data(),
+                }),
+            },
+        ]
+    }
+}
+
+fn starts_with(input: &[u8], Arguments { pattern, .. }: &Arguments, span: Span) -> Value {
+    Value::Bool {
+        val: input.starts_with(pattern),
+        span,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(BytesStartsWith {})
+    }
+}

crates/nu-command/src/default_context.rs

@@ -209,7 +209,8 @@ pub fn create_default_context(cwd: impl AsRef<Path>) -> EngineState {
 
         // Bytes
         bind_command! {
-            BytesLen
+            BytesLen,
+            BytesStartsWith
         }
 
         // FileSystem