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Std::str::from_utf8

As explained in Refactoring to Rust

std::str::from_utf8 is a Rust standard-library function that validates UTF-8 bytes and returns a string slice when they are valid.

std::str::from_utf8 validates a byte slice as UTF-8 and returns a Rust string slice when validation succeeds. In an NGINX HTTP handler, it turns the received request-body bytes into usable text while preserving error handling for invalid input. section 4.4.2

Reading an NGINX request body

After extracting the request-body buffer, validate it with std::str::from_utf8. A successful conversion produces a string slice containing the body, such as "3 4 * 2 -"; if errors are raised, the handler does not obtain valid text. section 4.4.2

How Refactoring to Rust covers it

How deep it goes
Explains validation and successful conversion, while leaving byte-buffer extraction and pointer arithmetic to surrounding code.
Examples
Demonstrates conversion of an NGINX request body containing "3 4 * 2 -" and verification through curl.
What it assumes
Assumes byte-slice extraction from FFI buffers and teaches the UTF-8 validity check that produces text.
What you can do after
Apply it in an NGINX HTTP handler to obtain validated request text from a byte slice.
How it connects
Connects UTF-8 validation with byte slices, string slices, raw pointers, lifetimes, and NGINX HTTP handlers.
Cover of Refactoring to Rust
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Related concepts

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