├── .gitignore ├── .vscode └── launch.json ├── Cargo.toml ├── LICENSE-APACHE ├── LICENSE-MIT ├── examples └── stm32f412-disco │ ├── .cargo │ └── config │ ├── .vscode │ ├── extensions.json │ ├── launch.json │ └── tasks.json │ ├── Cargo.toml │ ├── STM32F412.svd │ ├── memory.x │ └── src │ └── main.rs ├── readme.md └── src └── lib.rs /.gitignore: -------------------------------------------------------------------------------- 1 | /target 2 | Cargo.lock 3 | /examples/stm32f412-disco/target 4 | /examples/stm32f412-disco/.vscode/.cortex-debug* 5 | -------------------------------------------------------------------------------- /.vscode/launch.json: -------------------------------------------------------------------------------- 1 | { 2 | // Verwendet IntelliSense zum Ermitteln möglicher Attribute. 3 | // Zeigen Sie auf vorhandene Attribute, um die zugehörigen Beschreibungen anzuzeigen. 4 | // Weitere Informationen finden Sie unter https://go.microsoft.com/fwlink/?linkid=830387 5 | "version": "0.2.0", 6 | "configurations": [ 7 | { 8 | "type": "lldb", 9 | "request": "launch", 10 | "name": "Debug unit tests in library 'bformat'", 11 | "cargo": { 12 | "args": [ 13 | "test", 14 | "--no-run", 15 | "--lib", 16 | "--package=bformat" 17 | ], 18 | "filter": { 19 | "name": "bformat", 20 | "kind": "lib" 21 | } 22 | }, 23 | "args": [], 24 | "cwd": "${workspaceFolder}" 25 | } 26 | ] 27 | } -------------------------------------------------------------------------------- /Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | name = "arrform" 3 | version = "0.1.1" 4 | edition = "2021" 5 | license = "MIT OR Apache-2.0" 6 | description = "String formatting without memory allocator" 7 | repository = "https://github.com/Simsys/arrform" 8 | readme = "readme.md" 9 | keywords = ["no-std", "no-heap", "embedded", "string-formatting"] 10 | categories = ["no-std", "embedded", "value-formatting"] 11 | 12 | 13 | 14 | # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html 15 | 16 | [dependencies] 17 | 18 | -------------------------------------------------------------------------------- /LICENSE-APACHE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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IN NO EVENT 19 | SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY 20 | CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION 21 | OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR 22 | IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER 23 | DEALINGS IN THE SOFTWARE. -------------------------------------------------------------------------------- /examples/stm32f412-disco/.cargo/config: -------------------------------------------------------------------------------- 1 | [target.thumbv7m-none-eabi] 2 | # uncomment this to make `cargo run` execute programs on QEMU 3 | # runner = "qemu-system-arm -cpu cortex-m3 -machine lm3s6965evb -nographic -semihosting-config enable=on,target=native -kernel" 4 | 5 | [target.'cfg(all(target_arch = "arm", target_os = "none"))'] 6 | # uncomment ONE of these three option to make `cargo run` start a GDB session 7 | # which option to pick depends on your system 8 | # runner = "arm-none-eabi-gdb -q -x openocd.gdb" 9 | # runner = "gdb-multiarch -q -x openocd.gdb" 10 | # runner = "gdb -q -x openocd.gdb" 11 | 12 | rustflags = [ 13 | # This is needed if your flash or ram addresses are not aligned to 0x10000 in memory.x 14 | # See https://github.com/rust-embedded/cortex-m-quickstart/pull/95 15 | "-C", "link-arg=--nmagic", 16 | 17 | # LLD (shipped with the Rust toolchain) is used as the default linker 18 | "-C", "link-arg=-Tlink.x", 19 | 20 | # if you run into problems with LLD switch to the GNU linker by commenting out 21 | # this line 22 | # "-C", "linker=arm-none-eabi-ld", 23 | 24 | # if you need to link to pre-compiled C libraries provided by a C toolchain 25 | # use GCC as the linker by commenting out both lines above and then 26 | # uncommenting the three lines below 27 | # "-C", "linker=arm-none-eabi-gcc", 28 | # "-C", "link-arg=-Wl,-Tlink.x", 29 | # "-C", "link-arg=-nostartfiles", 30 | ] 31 | 32 | [build] 33 | # Pick ONE of these compilation targets 34 | # target = "thumbv6m-none-eabi" # Cortex-M0 and Cortex-M0+ 35 | # target = "thumbv7m-none-eabi" # Cortex-M3 36 | # target = "thumbv7em-none-eabi" # Cortex-M4 and Cortex-M7 (no FPU) 37 | target = "thumbv7em-none-eabihf" # Cortex-M4F and Cortex-M7F (with FPU) 38 | # target = "thumbv8m.base-none-eabi" # Cortex-M23 39 | # target = "thumbv8m.main-none-eabi" # Cortex-M33 (no FPU) 40 | # target = "thumbv8m.main-none-eabihf" # Cortex-M33 (with FPU) 41 | -------------------------------------------------------------------------------- /examples/stm32f412-disco/.vscode/extensions.json: -------------------------------------------------------------------------------- 1 | { 2 | // See https://go.microsoft.com/fwlink/?LinkId=827846 to learn about workspace recommendations. 3 | // Extension identifier format: ${publisher}.${name}. Example: vscode.csharp 4 | 5 | // List of extensions which should be recommended for users of this workspace. 6 | "recommendations": [ 7 | "vadimcn.vscode-lldb", 8 | "marus25.cortex-debug", 9 | "matklad.rust-analyzer", 10 | ], 11 | // List of extensions recommended by VS Code that should not be recommended for users of this workspace. 12 | "unwantedRecommendations": [ 13 | 14 | ] 15 | } -------------------------------------------------------------------------------- /examples/stm32f412-disco/.vscode/launch.json: -------------------------------------------------------------------------------- 1 | { 2 | // Use IntelliSense to learn about possible attributes. 3 | // Hover to view descriptions of existing attributes. 4 | // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387 5 | "version": "0.2.0", 6 | "configurations": [ 7 | { 8 | "type": "cortex-debug", 9 | "request": "launch", 10 | "name": "Debug (OpenOCD)", 11 | "servertype": "openocd", 12 | "cwd": "${workspaceRoot}", 13 | "preLaunchTask": "Cargo Build (debug)", 14 | "runToMain": true, 15 | "executable": "./target/thumbv7em-none-eabihf/debug/test_size", 16 | "device": "STM32F412ZGT6", 17 | "configFiles": [ 18 | "interface/stlink.cfg", 19 | "target/stm32f4x.cfg" 20 | ], 21 | "svdFile": "${workspaceRoot}/STM32F412.svd", 22 | }, 23 | { 24 | "type": "cortex-debug", 25 | "request": "launch", 26 | "name": "Run (OpenOCD)", 27 | "servertype": "openocd", 28 | "cwd": "${workspaceRoot}", 29 | "preLaunchTask": "Cargo Build (release)", 30 | "runToMain": true, 31 | "executable": "./target/thumbv7em-none-eabihf/release/test_size", 32 | "device": "STM32F412ZGT6", 33 | "configFiles": [ 34 | "interface/stlink.cfg", 35 | "target/stm32f4x.cfg" 36 | ], 37 | "svdFile": "${workspaceRoot}/STM32F412.svd", 38 | }, 39 | ] 40 | } -------------------------------------------------------------------------------- /examples/stm32f412-disco/.vscode/tasks.json: -------------------------------------------------------------------------------- 1 | { 2 | // See https://go.microsoft.com/fwlink/?LinkId=733558 3 | // for the documentation about the tasks.json format 4 | "version": "2.0.0", 5 | "tasks": [ 6 | { 7 | /* 8 | * This is the default cargo build task, 9 | * but we need to provide a label for it, 10 | * so we can invoke it from the debug launcher. 11 | */ 12 | "label": "Cargo Build (debug)", 13 | "type": "process", 14 | "command": "cargo", 15 | "args": ["build"], 16 | "problemMatcher": [ 17 | "$rustc" 18 | ], 19 | "group": { 20 | "kind": "build", 21 | "isDefault": true 22 | } 23 | }, 24 | { 25 | "label": "Cargo Build (release)", 26 | "type": "process", 27 | "command": "cargo", 28 | "args": ["build", "--release"], 29 | "problemMatcher": [ 30 | "$rustc" 31 | ], 32 | "group": "build" 33 | }, 34 | { 35 | "label": "Cargo Build Examples (debug)", 36 | "type": "process", 37 | "command": "cargo", 38 | "args": ["build","--examples"], 39 | "problemMatcher": [ 40 | "$rustc" 41 | ], 42 | "group": "build" 43 | }, 44 | { 45 | "label": "Cargo Build Examples (release)", 46 | "type": "process", 47 | "command": "cargo", 48 | "args": ["build","--examples", "--release"], 49 | "problemMatcher": [ 50 | "$rustc" 51 | ], 52 | "group": "build" 53 | }, 54 | { 55 | "label": "Cargo Clean", 56 | "type": "process", 57 | "command": "cargo", 58 | "args": ["clean"], 59 | "problemMatcher": [], 60 | "group": "build" 61 | }, 62 | ] 63 | } 64 | -------------------------------------------------------------------------------- /examples/stm32f412-disco/Cargo.toml: -------------------------------------------------------------------------------- 1 | [package] 2 | authors = ["Simsys "] 3 | edition = "2018" 4 | readme = "README.md" 5 | name = "test_size" 6 | version = "0.1.0" 7 | 8 | [dependencies] 9 | embedded-hal = "0.2" 10 | nb = "1" 11 | cortex-m = "0.7" 12 | cortex-m-rt = "0.6" 13 | panic-halt = "0.2" 14 | st7789 = "0.6.1" 15 | panic-semihosting = "0.5.6" 16 | embedded-graphics = "0.7.1" 17 | stm32f4xx-hal = { version = "0.10", features = ["rt", "stm32f412", "fsmc_lcd"] } 18 | arrform = { path = "/media/winni/1p4/Werkstatt/crates/arrform/" } 19 | 20 | [[bin]] 21 | name = "test_size" 22 | test = false 23 | bench = false 24 | 25 | [profile.dev] 26 | opt-level = 1 27 | codegen-units = 16 28 | debug = true 29 | lto = false 30 | 31 | [profile.release] 32 | opt-level = "s" # optimize for size 33 | codegen-units = 1 # better optimizations 34 | debug = true # symbols are nice and they don't increase the size on Flash 35 | lto = true # better optimizations 36 | -------------------------------------------------------------------------------- /examples/stm32f412-disco/memory.x: -------------------------------------------------------------------------------- 1 | MEMORY 2 | { 3 | FLASH : ORIGIN = 0x08000000, LENGTH = 1M 4 | RAM : ORIGIN = 0x20000000, LENGTH = 256K 5 | } 6 | 7 | /* This is where the call stack will be allocated. */ 8 | /* The stack is of the full descending type. */ 9 | /* NOTE Do NOT modify `_stack_start` unless you know what you are doing */ 10 | _stack_start = ORIGIN(RAM) + LENGTH(RAM); 11 | -------------------------------------------------------------------------------- /examples/stm32f412-disco/src/main.rs: -------------------------------------------------------------------------------- 1 | //! 2 | //! Demonstrates use of the Flexible Static Memory Controller to interface with an ST7789 LCD 3 | //! controller 4 | //! 5 | //! Hardware required: an STM32F412G-DISCO board 6 | //! 7 | //! Procedure: Compile this example, load it onto the microcontroller, and run it. 8 | //! 9 | //! Example run command: `cargo run --release --features stm32f412,rt,fsmc_lcd --example st7789-lcd` 10 | //! 11 | //! Expected behavior: The display shows a black background with four colored circles. Periodically, 12 | //! the color of each circle changes. 13 | //! 14 | //! Each circle takes a noticeable amount of time to draw, from top to bottom. Because 15 | //! embedded-graphics by default does not buffer anything in memory, it sends one pixel at a time 16 | //! to the LCD controller. The LCD interface can transfer rectangular blocks of pixels more quickly. 17 | //! 18 | 19 | #![no_std] 20 | #![no_main] 21 | 22 | use cortex_m_rt::entry; 23 | use panic_semihosting as _; 24 | 25 | use embedded_graphics::pixelcolor::Rgb565; 26 | use embedded_graphics::prelude::*; 27 | 28 | use st7789::ST7789; 29 | use stm32f4xx_hal::delay::Delay; 30 | use stm32f4xx_hal::fsmc_lcd::{ChipSelect1, FsmcLcd, LcdPins, Timing}; 31 | use stm32f4xx_hal::pac::{CorePeripherals, Peripherals}; 32 | use stm32f4xx_hal::prelude::*; 33 | 34 | #[entry] 35 | fn main() -> ! { 36 | let cp = CorePeripherals::take().unwrap(); 37 | let dp = Peripherals::take().unwrap(); 38 | 39 | let rcc = dp.RCC.constrain(); 40 | // Make HCLK faster to allow updating the display more quickly 41 | let clocks = rcc.cfgr.hclk(100.mhz()).freeze(); 42 | 43 | let mut delay = Delay::new(cp.SYST, &clocks); 44 | 45 | let gpiod = dp.GPIOD.split(); 46 | let gpioe = dp.GPIOE.split(); 47 | let gpiof = dp.GPIOF.split(); 48 | 49 | // Pins connected to the LCD on the 32F412GDISCOVERY board 50 | let lcd_pins = LcdPins { 51 | data: ( 52 | gpiod.pd14.into_alternate(), 53 | gpiod.pd15.into_alternate(), 54 | gpiod.pd0.into_alternate(), 55 | gpiod.pd1.into_alternate(), 56 | gpioe.pe7.into_alternate(), 57 | gpioe.pe8.into_alternate(), 58 | gpioe.pe9.into_alternate(), 59 | gpioe.pe10.into_alternate(), 60 | gpioe.pe11.into_alternate(), 61 | gpioe.pe12.into_alternate(), 62 | gpioe.pe13.into_alternate(), 63 | gpioe.pe14.into_alternate(), 64 | gpioe.pe15.into_alternate(), 65 | gpiod.pd8.into_alternate(), 66 | gpiod.pd9.into_alternate(), 67 | gpiod.pd10.into_alternate(), 68 | ), 69 | address: gpiof.pf0.into_alternate(), 70 | read_enable: gpiod.pd4.into_alternate(), 71 | write_enable: gpiod.pd5.into_alternate(), 72 | chip_select: ChipSelect1(gpiod.pd7.into_alternate()), 73 | }; 74 | let lcd_reset = gpiod.pd11.into_push_pull_output(); 75 | let mut backlight_control = gpiof.pf5.into_push_pull_output(); 76 | 77 | // Speed up timing settings, assuming HCLK is 100 MHz (1 cycle = 10 nanoseconds) 78 | // These read timings work to read settings, but slower timings are needed to read from the 79 | // frame memory. 80 | // Read timing: RD can go low at the same time as D/C changes and CS goes low. 81 | // RD must be low for at least 45 ns -> DATAST=8 82 | // Also, a read cycle must take at least 160 nanoseconds, so set ADDSET=8. This means 83 | // that a whole read takes 16 HCLK cycles (160 nanoseconds). 84 | // Bus turnaround time is zero, because no particular interval is required between transactions. 85 | let read_timing = Timing::default().data(8).address_setup(8).bus_turnaround(0); 86 | // Write timing: Minimum 10 nanoseconds from when WR goes high to CS goes high, so 87 | // HCLK can't be faster than 100 MHz. 88 | // NWE must be low for at least 15 ns -> DATAST=3 89 | // A write cycle must take at least 66 nanoseconds, so ADDSET=3. This means that a whole 90 | // write cycle takes 7 HCLK cycles (70 nanoseconds) (an extra HCLK cycle is added after NWE 91 | // goes high). 92 | // Bus turnaround time is zero, because no particular interval is required between transactions. 93 | let write_timing = Timing::default().data(3).address_setup(3).bus_turnaround(0); 94 | 95 | let (_fsmc, interface) = FsmcLcd::new(dp.FSMC, lcd_pins, &read_timing, &write_timing); 96 | 97 | // The 32F412GDISCOVERY board has an FRD154BP2902-CTP LCD. There is no easily available 98 | // datasheet, so the behavior of this code is based on the working demonstration C code: 99 | // https://github.com/STMicroelectronics/STM32CubeF4/blob/e084518f363e04344dc37822210a75e87377b200/Drivers/BSP/STM32412G-Discovery/stm32412g_discovery_lcd.c 100 | // https://github.com/STMicroelectronics/STM32CubeF4/blob/e084518f363e04344dc37822210a75e87377b200/Drivers/BSP/Components/st7789h2/st7789h2.c 101 | 102 | // Add LCD controller driver 103 | let mut lcd = ST7789::new(interface, lcd_reset, 240, 240); 104 | // Initialise the display, clear the screen and turn on the backlight 105 | lcd.init(&mut delay).unwrap(); 106 | lcd.clear(Rgb565::BLACK).unwrap(); 107 | backlight_control.set_high(); 108 | 109 | use embedded_graphics::{ mono_font:: 110 | { MonoTextStyleBuilder, iso_8859_1::FONT_10X20 }, 111 | text::Text, 112 | }; 113 | use arrform::{ArrForm, arrform}; 114 | 115 | let style = MonoTextStyleBuilder::new() 116 | .font(&FONT_10X20) 117 | .text_color(Rgb565::CSS_LIGHT_GRAY) 118 | .build(); 119 | 120 | let mut f: f32 = 1.0; 121 | 122 | loop { 123 | lcd.clear(Rgb565::BLACK).unwrap(); 124 | 125 | let s = "no number"; 126 | // let s = arrform!(64, "int {}", f as u32); 127 | // let s = arrform!(64, "float {:.1}", f); 128 | 129 | Text::new(s, Point::new(40, 40), style).draw(&mut lcd).unwrap(); 130 | delay.delay_ms(1000_u32); 131 | f += 1.0; 132 | } 133 | } 134 | -------------------------------------------------------------------------------- /readme.md: -------------------------------------------------------------------------------- 1 | String formatting without memory allocator 2 | ========================================== 3 | 4 | In bare matal systems, there is often the task of converting numbers into text and formatting 5 | them. The standard Rust functions like format!, write! etc. cannot be used in no_std 6 | environments because they require a memory allocator. The arrform! macro uses the standard 7 | library functions, but writes to a fixed length array which is alocated on the stack. 8 | 9 | This crate is usable in no_std environments. This is a replacement for the format! macro, based 10 | on a fixed-size array allocated on the stack. 11 | 12 | # arrform! 13 | 14 | ``` rust 15 | use arrform::{arrform, ArrForm}; 16 | 17 | let af = arrform!(64, "write some stuff {}: {:.2}", "foo", 42.3456); 18 | assert_eq!("write some stuff foo: 42.35", af.as_str()); 19 | ``` 20 | 21 | ## ArrForm struct as an alternative 22 | 23 | The ArrForm struct provides more detailed error handling and supports multiple use of the 24 | same buffer. However, it is much more cumbersome to use and generates more syntactic noise. 25 | 26 | # Overhead 27 | 28 | The convenient option to format can cost a lot of storage space. On a Cortex M4 992 bytes of 29 | program code are needed additionally, if instead of a simple string a simple u32 number is 30 | embedded with the help of the macro. It becomes even more expensive if f32 numbers are output 31 | formatted (30,928 bytes additional). The program code used to determine these numbers can be 32 | found in the example directory. 33 | 34 | Looking for an alternative that wastes less memory? The Crate [tfmt](https://github.com/Simsys/tfmt) 35 | can be used as an alternative in most cases. This crate has the additional advantages that it 36 | is guaranteed not to contain any panic branches and also works much more efficiently. 37 | 38 | # License 39 | 40 | Apache version 2.0 or Mit 41 | -------------------------------------------------------------------------------- /src/lib.rs: -------------------------------------------------------------------------------- 1 | #![no_std] 2 | 3 | //! String formatting without memory allocator 4 | //! ========================================== 5 | //! 6 | //! In bare metal systems, there is often the task of converting numbers into text and formatting 7 | //! them. The standard Rust functions like format!, write! etc. cannot be used in no_std 8 | //! environments because they require a memory allocator. The arrform! macro uses the standard 9 | //! library functions, but writes to a fixed length array which is alocated on the stack. 10 | //! 11 | //! This crate is usable in no_std environments. This is a replacement for the format! macro, based 12 | //! on a fixed-size array allocated on the stack. 13 | //! 14 | //! # arrform! 15 | //! 16 | //! ``` rust 17 | //! use arrform::arrform; 18 | //! 19 | //! let af = arrform!(64, "write some stuff {}: {:.2}", "foo", 42.3456); 20 | //! assert_eq!("write some stuff foo: 42.35", af.as_str()); 21 | //! ``` 22 | //! 23 | //! ## ArrForm struct as an alternative 24 | //! 25 | //! The [ArrForm] struct provides more detailed error handling and supports multiple use of the 26 | //! same buffer. However, it is much more cumbersome to use and generates more syntactic noise. 27 | //! 28 | //! # Overhead 29 | //! 30 | //! The convenient option to format can cost a lot of storage space. On a Cortex M4 992 bytes of 31 | //! program code are needed additionally, if instead of a simple string a simple u32 number is 32 | //! embedded with the help of the macro. It becomes even more expensive if f32 numbers are output 33 | //! formatted (30,928 bytes additional). The program code used to determine these numbers can be 34 | //! found in the example directory. 35 | //! 36 | //! # License 37 | //! 38 | //! Apache version 2.0 or Mit 39 | //! 40 | use core::{fmt, str::from_utf8_unchecked}; 41 | use core::mem::MaybeUninit; 42 | 43 | #[allow(unused_imports)] 44 | use core::format_args; 45 | 46 | /// Generates formatted text in a buffer on the stack 47 | /// 48 | /// Allows precise handling of errors. A buffer created once can be used several times. The 49 | /// application requires more typing and contains some syntactic noise. 50 | /// ``` 51 | /// use arrform::ArrForm; 52 | /// 53 | /// let mut af = ArrForm::<64>::new(); 54 | /// match af.format(format_args!("write some stuff {}: {:.2}", "foo", 42.3456)) { 55 | /// Ok(()) => { 56 | /// assert_eq!("write some stuff foo: 42.35", af.as_str()); 57 | /// assert_eq!(b"write some stuff foo: 42.35", af.as_bytes()); 58 | /// }, 59 | /// Err(_) => { 60 | /// panic!("An error occurred"); 61 | /// } 62 | /// } 63 | /// 64 | /// // Use the buffer a second time 65 | /// af.format( 66 | /// format_args!("same buffer, new {}, int {}, float {:.1}", "text", 123, 4.1234) 67 | /// ).unwrap(); 68 | /// 69 | /// assert_eq!("same buffer, new text, int 123, float 4.1", af.as_str()); 70 | /// ``` 71 | pub struct ArrForm { 72 | buffer: [u8; BUF_SIZE], 73 | used: usize, 74 | } 75 | 76 | impl ArrForm { 77 | 78 | /// Creates new buffer on the stack 79 | pub fn new() -> Self { 80 | // We don't need to initialize, because we write before we read 81 | let buffer: [u8; BUF_SIZE] = unsafe { MaybeUninit::uninit().assume_init() }; 82 | ArrForm { buffer, used: 0 } 83 | } 84 | 85 | /// Format numbers and strings 86 | pub fn format(&mut self, args: fmt::Arguments) -> fmt::Result { 87 | self.used = 0; // if format is used several times 88 | fmt::write(self, args) 89 | } 90 | 91 | /// Get a reference to the result as a slice inside the buffer as str 92 | pub fn as_str(&self) -> &str { 93 | // We are really sure, that the buffer contains only valid utf8 characters 94 | unsafe { from_utf8_unchecked(&self.buffer[..self.used]) } 95 | } 96 | 97 | /// Get a reference to the result as a slice inside the buffer as bytes 98 | pub fn as_bytes(&self) -> &[u8] { 99 | &self.buffer[..self.used] 100 | } 101 | } 102 | 103 | impl fmt::Write for ArrForm { 104 | 105 | fn write_str(&mut self, s: &str) -> fmt::Result { 106 | let remaining_buf = &mut self.buffer[self.used..]; 107 | let raw_s = s.as_bytes(); 108 | 109 | // Treat imminent buffer overflow 110 | if raw_s.len() > remaining_buf.len() { 111 | remaining_buf.copy_from_slice(&raw_s[..remaining_buf.len()]); 112 | self.used += remaining_buf.len(); 113 | Err(fmt::Error) 114 | } else { 115 | remaining_buf[..raw_s.len()].copy_from_slice(raw_s); 116 | self.used += raw_s.len(); 117 | Ok(()) 118 | } 119 | } 120 | } 121 | 122 | /// A macro to format numbers into text, based on a fixed-size array allocated on the stack 123 | /// 124 | /// This macro first reserves a buffer on the stack. Then it uses the struct [ArrForm] to format 125 | /// text and numbers. It returns an instance of ArrForm that allows easy access to the contained 126 | /// text. The macro panics if the buffer is chosen too small. 127 | /// 128 | /// ``` 129 | /// use arrform::arrform; 130 | /// 131 | /// let af = arrform!(64, "write some {}, int {}, float {:.3}", "stuff", 4711, 3.1415); 132 | /// assert_eq!("write some stuff, int 4711, float 3.142", af.as_str()); 133 | /// ``` 134 | #[macro_export] 135 | macro_rules! arrform { 136 | ($size:expr, $($arg:tt)*) => {{ 137 | let mut af = $crate::ArrForm::<$size>::new(); 138 | 139 | // Panic on buffer overflow 140 | af.format(format_args!($($arg)*)).expect("Buffer overflow"); 141 | af 142 | }} 143 | } 144 | --------------------------------------------------------------------------------