visa-sys

FFI bindings to the VISA (Virtual Instrument Software Architecture) library.

The crate ships pre-generated bindings, so a C toolchain / libclang is not required for a normal build. The VISA runtime itself (NI-VISA, Keysight, R&S, …) must be available on the target machine.

Linking modes

Default: link at build time

By default the crate links the system VISA library at build time. The library name and search path are chosen per platform and can be overridden with environment variables:

Variable	Purpose
`LIB_VISA_NAME`	Override the library name passed to the linker.
`LIB_VISA_PATH`	Add a library search path (a framework on macOS).
`INCLUDE_VISA_PATH`	Header directory used when regenerating with `bindgen`.

Enable the bindgen feature to regenerate the bindings from visa.h at build time instead of using the checked-in ones.

`dynamic_load`: load at run time

[dependencies]
visa-sys = { version = "0.1", features = ["dynamic_load"] }

With the dynamic_load feature the VISA shared library is not linked at build time. Instead it is opened at run time with libloading, so the same binary can run on machines with or without VISA installed. The free functions (viOpenDefaultRM, viOpen, …) keep the same signatures as the linked build, so switching modes needs no code changes.

use visa_sys::*;

// The library auto-loads from the platform default path on the first call:
let mut session = 0;
let status = unsafe { viOpenDefaultRM(&mut session as ViPSession) };

// …or load it explicitly to handle a missing runtime without panicking:
if let Err(e) = load_visa_library() {
    eprintln!("VISA not available: {e}");
}
// A custom path is also supported:
// load_visa_library_from_path("/opt/visa/libvisa.so")?;

Default search names: VISA.framework/VISA (macOS), visa64.dll / visa32.dll (Windows), libvisa.so (other).

Behaviour and limitations

Auto-load panics on a missing library. A VISA call auto-loads on first use and panics if the default path cannot be opened — analogous to a linked build failing to start. Call load_visa_library() first to detect this gracefully.
Tolerant of partial implementations. Symbols are resolved lazily; a VISA runtime that omits a rarely-used function still works for the functions it does export. Calling an unsupported function panics at the call site.
No variadic helpers. viPrintf, viSPrintf, viScanf, viSScanf and viQueryf are unavailable as free functions (a C-variadic function cannot be called through a function pointer). Use the explicit-va_list variants viVPrintf, viVSPrintf, viVScanf, viVSScanf, viVQueryf.

Note: regenerating the dynamic bindings with --features "bindgen dynamic_load" should be done on Linux or Windows. On macOS bindgen prefixes the resolved symbol names with an underscore, which dlsym does not expect; the checked-in src/prebind/bindings_dynamic.rs uses the portable bare names.

License

Licensed under either of MIT or Apache-2.0 at your option.