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113 lines
3.5 KiB
Markdown
113 lines
3.5 KiB
Markdown
# "file" sample introduction
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This sample demonstrates the supported file interaction API of WASI.
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This sample can also demonstrate the SGX IPFS (Intel Protected File System), enabling an enclave to seal and unseal data at rest.
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## Preparation
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Please install WASI SDK, download the [wasi-sdk release](https://github.com/WebAssembly/wasi-sdk/releases) and extract the archive to default path `/opt/wasi-sdk`.
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For testing with SGX IPFS, follow the instructions in [the documentation of SGX for WAMR](../../doc/linux_sgx.md#sgx-intel-protected-file-system).
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## Build the sample
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```bash
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mkdir build
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cd build
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cmake ..
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make
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```
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The WebAssembly application is the file located at `wasm-app/file.wasm`.
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## Run workload
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Either use [iwasm-sample](../../product-mini/platforms/linux/) for Linux, or [enclave-sample](../../product-mini/platforms/linux-sgx/enclave-sample/) for Intel SGX to run the sample, with the argument to allow the file system interaction with the current folder (`--dir=.`).
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The output with Linux and POSIX is like:
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```bash
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Opening a file..
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[Test] File opening passed.
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Writing to the file..
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[Test] File writing passed.
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Moving the cursor to the start of the file..
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Reading from the file, up to 1000 characters..
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Text read: Hello, world!
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[Test] File reading passed.
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Determine whether we reach the end of the file..
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Is the end of file? 1
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[Test] End of file detection passed.
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Getting the plaintext size..
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The plaintext size is 13.
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[Test] Retrieving file offset passed.
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Force actual write of all the cached data to the disk..
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[Test] Retrieving file offset passed.
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Writing 5 characters at offset 7..
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File current offset: 13
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[Test] Writing at specified offset passed.
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Reading 5 characters at offset 7..
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Text read: James
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File current offset: 13
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[Test] Reading at specified offset passed.
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Allocate more space to the file..
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File current offset: 13
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Moving to the end..
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File current offset: 23
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[Test] Allocation or more space passed.
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Extend the file size of 10 bytes using ftruncate..
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File current offset: 23
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Moving to the end..
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File current offset: 33
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[Test] Extension of the file size passed.
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Closing from the file..
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[Test] Closing file passed.
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Getting the size of the file on disk..
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The file size is 33.
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All the tests passed!
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```
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The output with SGX and IPFS is like:
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```bash
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Opening a file..
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[Test] File opening passed.
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Writing to the file..
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[Test] File writing passed.
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Moving the cursor to the start of the file..
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Reading from the file, up to 1000 characters..
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Text read: Hello, world!
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[Test] File reading passed.
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Determine whether we reach the end of the file..
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Is the end of file? 1
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[Test] End of file detection passed.
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Getting the plaintext size..
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The plaintext size is 13.
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[Test] Retrieving file offset passed.
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Force actual write of all the cached data to the disk..
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[Test] Retrieving file offset passed.
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Writing 5 characters at offset 7..
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File current offset: 13
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[Test] Writing at specified offset passed.
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Reading 5 characters at offset 7..
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Text read: James
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File current offset: 13
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[Test] Reading at specified offset passed.
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Allocate more space to the file..
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File current offset: 23
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Moving to the end..
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File current offset: 23
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[Test] Allocation or more space passed.
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Extend the file size of 10 bytes using ftruncate..
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File current offset: 23
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Moving to the end..
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File current offset: 33
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[Test] Extension of the file size passed.
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Closing from the file..
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[Test] Closing file passed.
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Getting the size of the file on disk..
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The file size is 4096.
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All the tests passed!
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```
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For SGX IPFS, refer to [SGX Intel Protected File System](../../doc/linux_sgx.md#sgx-intel-protected-file-system) for more details.
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