add more bytes cmd (#5989)

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

@@ -0,0 +1,281 @@
+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, Example, PipelineData, ShellError, Signature, Span, SyntaxShape, Value,
+};
+use std::cmp::Ordering;
+
+#[derive(Clone)]
+pub struct BytesAt;
+
+struct Arguments {
+    start: isize,
+    end: isize,
+    arg_span: Span,
+    column_paths: Option<Vec<CellPath>>,
+}
+
+impl BytesArgument for Arguments {
+    fn take_column_paths(&mut self) -> Option<Vec<CellPath>> {
+        self.column_paths.take()
+    }
+}
+
+/// ensure given `range` is valid, and returns [start, end, val_span] pair.
+fn parse_range(range: Value, head: Span) -> Result<(isize, isize, Span), ShellError> {
+    let (start, end, span) = match range {
+        Value::List { mut vals, span } => {
+            if vals.len() != 2 {
+                return Err(ShellError::UnsupportedInput(
+                    "More than two indices given".to_string(),
+                    span,
+                ));
+            } else {
+                let end = vals.pop().expect("Already check has size 2");
+                let end = match end {
+                    Value::Int { val, .. } => val.to_string(),
+                    Value::String { val, .. } => val,
+                    other => {
+                        return Err(ShellError::UnsupportedInput(
+                            "could not perform subbytes. Expecting a string or int".to_string(),
+                            other.span().unwrap_or(head),
+                        ))
+                    }
+                };
+                let start = vals.pop().expect("Already check has size 1");
+                let start = match start {
+                    Value::Int { val, .. } => val.to_string(),
+                    Value::String { val, .. } => val,
+                    other => {
+                        return Err(ShellError::UnsupportedInput(
+                            "could not perform subbytes. Expecting a string or int".to_string(),
+                            other.span().unwrap_or(head),
+                        ))
+                    }
+                };
+                (start, end, span)
+            }
+        }
+        Value::String { val, span } => {
+            let splitted_result = val.split_once(',');
+            match splitted_result {
+                Some((start, end)) => (start.to_string(), end.to_string(), span),
+                None => {
+                    return Err(ShellError::UnsupportedInput(
+                        "could not perform subbytes".to_string(),
+                        span,
+                    ))
+                }
+            }
+        }
+        other => {
+            return Err(ShellError::UnsupportedInput(
+                "could not perform subbytes".to_string(),
+                other.span().unwrap_or(head),
+            ))
+        }
+    };
+
+    let start: isize = if start.is_empty() || start == "_" {
+        0
+    } else {
+        match start.trim().parse() {
+            Ok(s) => s,
+            Err(_) => {
+                return Err(ShellError::UnsupportedInput(
+                    "could not perform subbytes".to_string(),
+                    span,
+                ))
+            }
+        }
+    };
+    let end: isize = if end.is_empty() || end == "_" {
+        isize::max_value()
+    } else {
+        match end.trim().parse() {
+            Ok(s) => s,
+            Err(_) => {
+                return Err(ShellError::UnsupportedInput(
+                    "could not perform subbytes".to_string(),
+                    span,
+                ))
+            }
+        }
+    };
+    Ok((start, end, span))
+}
+
+impl Command for BytesAt {
+    fn name(&self) -> &str {
+        "bytes at"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("bytes at")
+            .required("range", SyntaxShape::Any, "the indexes to get bytes")
+            .rest(
+                "rest",
+                SyntaxShape::CellPath,
+                "optionally get bytes by column paths",
+            )
+            .category(Category::Bytes)
+    }
+
+    fn usage(&self) -> &str {
+        "Get bytes defined by a range. Note that the start is included but the end is excluded, and that the first byte is index 0."
+    }
+
+    fn search_terms(&self) -> Vec<&str> {
+        vec!["slice"]
+    }
+
+    fn run(
+        &self,
+        engine_state: &EngineState,
+        stack: &mut Stack,
+        call: &Call,
+        input: PipelineData,
+    ) -> Result<PipelineData, ShellError> {
+        let range: Value = call.req(engine_state, stack, 0)?;
+        let (start, end, arg_span) = parse_range(range, call.head)?;
+        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 {
+            start,
+            end,
+            arg_span,
+            column_paths,
+        };
+        operate(at, arg, input, call.head, engine_state.ctrlc.clone())
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Get a subbytes `0x[10 01]` from the bytes `0x[33 44 55 10 01 13]`",
+                example: " 0x[33 44 55 10 01 13] | bytes at [3 4]",
+                result: Some(Value::Binary {
+                    val: vec![0x10],
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description: "Alternatively, you can use the form",
+                example: " 0x[33 44 55 10 01 13] | bytes at '3,4'",
+                result: Some(Value::Binary {
+                    val: vec![0x10],
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description: "Drop the last `n` characters from the string",
+                example: " 0x[33 44 55 10 01 13] | bytes at ',-3'",
+                result: Some(Value::Binary {
+                    val: vec![0x33, 0x44, 0x55],
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description: "Get the remaining characters from a starting index",
+                example: " 0x[33 44 55 10 01 13] | bytes at '3,'",
+                result: Some(Value::Binary {
+                    val: vec![0x10, 0x01, 0x13],
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description: "Get the characters from the beginning until ending index",
+                example: " 0x[33 44 55 10 01 13] | bytes at ',4'",
+                result: Some(Value::Binary {
+                    val: vec![0x33, 0x44, 0x55, 0x10],
+                    span: Span::test_data(),
+                }),
+            },
+            Example {
+                description:
+                    "Or the characters from the beginning until ending index inside a table",
+                example: r#" [[ColA ColB ColC]; [0x[11 12 13] 0x[14 15 16] 0x[17 18 19]]] | bytes at "1," ColB ColC"#,
+                result: Some(Value::List {
+                    vals: vec![Value::Record {
+                        cols: vec!["ColA".to_string(), "ColB".to_string(), "ColC".to_string()],
+                        vals: vec![
+                            Value::Binary {
+                                val: vec![0x11, 0x12, 0x13],
+                                span: Span::test_data(),
+                            },
+                            Value::Binary {
+                                val: vec![0x15, 0x16],
+                                span: Span::test_data(),
+                            },
+                            Value::Binary {
+                                val: vec![0x18, 0x19],
+                                span: Span::test_data(),
+                            },
+                        ],
+                        span: Span::test_data(),
+                    }],
+                    span: Span::test_data(),
+                }),
+            },
+        ]
+    }
+}
+
+fn at(input: &[u8], arg: &Arguments, span: Span) -> Value {
+    let len: isize = input.len() as isize;
+
+    let start: isize = if arg.start < 0 {
+        arg.start + len
+    } else {
+        arg.start
+    };
+    let end: isize = if arg.end < 0 {
+        std::cmp::max(len + arg.end, 0)
+    } else {
+        arg.end
+    };
+
+    if start < len && end >= 0 {
+        match start.cmp(&end) {
+            Ordering::Equal => Value::Binary { val: vec![], span },
+            Ordering::Greater => Value::Error {
+                error: ShellError::UnsupportedInput(
+                    "End must be greater than or equal to Start".to_string(),
+                    arg.arg_span,
+                ),
+            },
+            Ordering::Less => Value::Binary {
+                val: {
+                    let input_iter = input.iter().copied().skip(start as usize);
+                    if end == isize::max_value() {
+                        input_iter.collect()
+                    } else {
+                        input_iter.take((end - start) as usize).collect()
+                    }
+                },
+                span,
+            },
+        }
+    } else {
+        Value::Binary { val: vec![], span }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_examples() {
+        use crate::test_examples;
+
+        test_examples(BytesAt {})
+    }
+}