InstructionTextBuffer is only present with alloc (new crate flag)

2 files changed, 96 insertions, 85 deletions

diff --git a/src/long_mode/display.rs b/src/long_mode/display.rs
index e8000ed..9d9b7bb 100644
--- a/src/long_mode/display.rs
+++ b/src/long_mode/display.rs
@@ -4273,97 +4273,106 @@ impl<'a, F: DisplaySink> crate::long_mode::OperandVisitor for RelativeBranchPrin
     }
 }
 
-/// helper to format `amd64` instructions with highest throughput and least configuration. this is
-/// functionally a buffer for one x86 instruction's text.
-///
-/// ### when to use this over `fmt::Display`?
-///
-/// `fmt::Display` is a fair choice in most cases. in some cases, `InstructionTextBuffer` may
-/// support formatting options that may be difficult to configure for a `Display` impl.
-/// additionally, `InstructionTextBuffer` may be able to specialize more effectively where
-/// `fmt::Display`, writing to a generic `fmt::Write`, may not.
-///
-/// if your use case for `yaxpeax-x86` involves being bounded on the speed of disassembling and
-/// formatting instructions, [`InstructionTextBuffer::format_inst`] has been measured as up to 11%
-/// faster than an equivalent `write!(buf, "{}", inst)`.
-///
-/// `InstructionTextBuffer` involves internal allocations; if your use case for `yaxpeax-x86`
-/// requires allocations never occurring, it is not an appropriate tool.
-///
-/// ### example
-///
-/// ```
-/// use yaxpeax_x86::long_mode::InstDecoder;
-/// use yaxpeax_x86::long_mode::InstructionTextBuffer;
-/// use yaxpeax_x86::long_mode::DisplayStyle;
-///
-/// let bytes = &[0x33, 0xc0];
-/// let inst = InstDecoder::default().decode_slice(bytes).expect("can decode");
-/// let mut text_buf = InstructionTextBuffer::new();
-/// assert_eq!(
-///     text_buf.format_inst(&inst.display_with(DisplayStyle::Intel)).expect("can format"),
-///     "xor eax, eax"
-/// );
-///
-/// // or, getting the formatted instruction with `text_str`:
-/// assert_eq!(
-///     text_buf.text_str(),
-///     "xor eax, eax"
-/// );
-/// ```
-pub struct InstructionTextBuffer {
-    content: alloc::string::String,
-}
-
-impl InstructionTextBuffer {
-    /// create an `InstructionTextBuffer` with default settings. `InstructionTextBuffer`'s default
-    /// settings format instructions identically to their corresponding `fmt::Display`.
-    pub fn new() -> Self {
-        let mut buf = alloc::string::String::new();
-        // TODO: move 512 out to a MAX_INSTRUCTION_LEN const and appropriate justification (and
-        // fuzzing and ..)
-        buf.reserve(512);
-        Self {
-            content: buf,
-        }
-    }
+#[cfg(feature="alloc")]
+mod buffer_sink {
+    use core::fmt;
+    use super::super::{DisplayStyle, InstructionDisplayer};
+    use super::{contextualize_c, contextualize_intel};
 
-    /// format `inst` into this buffer. returns a borrow of that same internal buffer for convenience.
+    /// helper to format `amd64` instructions with highest throughput and least configuration. this is
+    /// functionally a buffer for one x86 instruction's text.
+    ///
+    /// ### when to use this over `fmt::Display`?
+    ///
+    /// `fmt::Display` is a fair choice in most cases. in some cases, `InstructionTextBuffer` may
+    /// support formatting options that may be difficult to configure for a `Display` impl.
+    /// additionally, `InstructionTextBuffer` may be able to specialize more effectively where
+    /// `fmt::Display`, writing to a generic `fmt::Write`, may not.
+    ///
+    /// if your use case for `yaxpeax-x86` involves being bounded on the speed of disassembling and
+    /// formatting instructions, [`InstructionTextBuffer::format_inst`] has been measured as up to 11%
+    /// faster than an equivalent `write!(buf, "{}", inst)`.
     ///
-    /// this clears and reuses an internal buffer; if an instruction had been previously formatted
-    /// through this buffer, it will be overwritten.
-    pub fn format_inst<'buf, 'instr>(&'buf mut self, display: &InstructionDisplayer<'instr>) -> Result<&'buf str, fmt::Error> {
-        // Safety: this sink is used to format exactly one instruction and then dropped. it can
-        // never escape `format_inst`.
-        let mut handle = unsafe { self.write_handle() };
+    /// `InstructionTextBuffer` involves internal allocations; if your use case for `yaxpeax-x86`
+    /// requires allocations never occurring, it is not an appropriate tool.
+    ///
+    /// ### example
+    ///
+    /// ```
+    /// use yaxpeax_x86::long_mode::InstDecoder;
+    /// use yaxpeax_x86::long_mode::InstructionTextBuffer;
+    /// use yaxpeax_x86::long_mode::DisplayStyle;
+    ///
+    /// let bytes = &[0x33, 0xc0];
+    /// let inst = InstDecoder::default().decode_slice(bytes).expect("can decode");
+    /// let mut text_buf = InstructionTextBuffer::new();
+    /// assert_eq!(
+    ///     text_buf.format_inst(&inst.display_with(DisplayStyle::Intel)).expect("can format"),
+    ///     "xor eax, eax"
+    /// );
+    ///
+    /// // or, getting the formatted instruction with `text_str`:
+    /// assert_eq!(
+    ///     text_buf.text_str(),
+    ///     "xor eax, eax"
+    /// );
+    /// ```
+    pub struct InstructionTextBuffer {
+        content: alloc::string::String,
+    }
 
-        match display.style {
-            DisplayStyle::Intel => {
-                contextualize_intel(&display.instr, &mut handle)?;
-            }
-            DisplayStyle::C => {
-                contextualize_c(&display.instr, &mut handle)?;
+    impl InstructionTextBuffer {
+        /// create an `InstructionTextBuffer` with default settings. `InstructionTextBuffer`'s default
+        /// settings format instructions identically to their corresponding `fmt::Display`.
+        pub fn new() -> Self {
+            let mut buf = alloc::string::String::new();
+            // TODO: move 512 out to a MAX_INSTRUCTION_LEN const and appropriate justification (and
+            // fuzzing and ..)
+            buf.reserve(512);
+            Self {
+                content: buf,
             }
         }
 
-        Ok(self.text_str())
-    }
+        /// format `inst` into this buffer. returns a borrow of that same internal buffer for convenience.
+        ///
+        /// this clears and reuses an internal buffer; if an instruction had been previously formatted
+        /// through this buffer, it will be overwritten.
+        pub fn format_inst<'buf, 'instr>(&'buf mut self, display: &InstructionDisplayer<'instr>) -> Result<&'buf str, fmt::Error> {
+            // Safety: this sink is used to format exactly one instruction and then dropped. it can
+            // never escape `format_inst`.
+            let mut handle = unsafe { self.write_handle() };
 
-    /// return a borrow of the internal buffer. if an instruction has been formatted, the
-    /// returned `&str` contains that instruction's buffered text.
-    pub fn text_str(&self) -> &str {
-        self.content.as_str()
-    }
+            match display.style {
+                DisplayStyle::Intel => {
+                    contextualize_intel(&display.instr, &mut handle)?;
+                }
+                DisplayStyle::C => {
+                    contextualize_c(&display.instr, &mut handle)?;
+                }
+            }
 
-    /// do the necessary bookkeeping and provide an `InstructionTextSink` to write an instruction
-    /// into.
-    ///
-    /// SAFETY: callers must print at most one instruction into this handle.
-    unsafe fn write_handle(&mut self) -> yaxpeax_arch::display::InstructionTextSink {
-        self.content.clear();
-        // Safety: `content` was just cleared, so writing begins at the start of the buffer.
-        // `content`is large enough to hold a fully-formatted instruction (see
-        // `InstructionTextBuffer::new`).
-        yaxpeax_arch::display::InstructionTextSink::new(&mut self.content)
+            Ok(self.text_str())
+        }
+
+        /// return a borrow of the internal buffer. if an instruction has been formatted, the
+        /// returned `&str` contains that instruction's buffered text.
+        pub fn text_str(&self) -> &str {
+            self.content.as_str()
+        }
+
+        /// do the necessary bookkeeping and provide an `InstructionTextSink` to write an instruction
+        /// into.
+        ///
+        /// SAFETY: callers must print at most one instruction into this handle.
+        unsafe fn write_handle(&mut self) -> yaxpeax_arch::display::InstructionTextSink {
+            self.content.clear();
+            // Safety: `content` was just cleared, so writing begins at the start of the buffer.
+            // `content`is large enough to hold a fully-formatted instruction (see
+            // `InstructionTextBuffer::new`).
+            yaxpeax_arch::display::InstructionTextSink::new(&mut self.content)
+        }
     }
 }
+#[cfg(feature="alloc")]
+pub use buffer_sink::InstructionTextBuffer;
diff --git a/src/long_mode/mod.rs b/src/long_mode/mod.rs
index d66f59a..2ccbc22 100644
--- a/src/long_mode/mod.rs
+++ b/src/long_mode/mod.rs
@@ -7,7 +7,9 @@ pub mod uarch;
 pub use crate::MemoryAccessSize;
 
 #[cfg(feature = "fmt")]
-pub use self::display::{DisplayStyle, InstructionDisplayer, InstructionTextBuffer};
+pub use self::display::{DisplayStyle, InstructionDisplayer};
+#[cfg(all(feature = "fmt", feature = "alloc"))]
+pub use self::display::InstructionTextBuffer;
 
 use core::cmp::PartialEq;
 use crate::safer_unchecked::unreachable_kinda_unchecked as unreachable_unchecked;