Merging upstream version 0.12.2.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 97 insertions, 0 deletions

diff --git a/src/third-party/prqlc-c/README.md b/src/third-party/prqlc-c/README.md
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+# PRQL C library
+
+## Description
+
+This module compiles PRQL as a library (both `.a` and `.so` are generated). This
+allows embedding in languages that support FFI — for example, Golang.
+
+## Linking
+
+Copy the `.a` and `.so` files in a convenient place and add the following
+compile flags to Go (cgo):
+
+`CGO_LDFLAGS="-L/path/to/libprqlc_c.a -lprqlc -pthread -ldl" go build`
+
+## Examples
+
+Below is an example from an actual application that is using PRQL in Go.
+
+```go
+package prql
+
+/*
+
+
+#include <stdlib.h>
+
+int to_sql(char *prql_query, char *sql_query);
+int to_json(char *prql_query, char *json_query);
+
+*/
+import "C"
+
+import (
+    "errors"
+    "strings"
+    "unsafe"
+)
+
+// ToSQL converts a PRQL query to SQL
+func ToSQL(prql string) (string, error) {
+    // buffer length should not be less than 1K because we may get an error
+    // from the PRQL compiler with a very short query
+    cStringBufferLength := 1024
+
+    // allocate a buffer 3 times the length of the PRQL query to store the
+    // generated SQL query
+    if len(prql)*3 > cStringBufferLength {
+        cStringBufferLength = len(prql) * 3
+    }
+
+    // preallocate the buffer
+    cstr := C.CString(strings.Repeat(" ", cStringBufferLength))
+    defer C.free(unsafe.Pointer(cstr))
+
+    // convert the PRQL query to SQL
+    res := C.to_sql(C.CString(prql), cstr)
+    if res == 0 {
+        return C.GoString(cstr), nil
+    }
+
+    return "", errors.New(C.GoString(cstr))
+}
+
+// ToJSON converts a PRQL query to JSON
+func ToJSON(prql string) (string, error) {
+    // buffer length should not be less than 1K because we may get an error
+    cStringBufferLength := 1024
+    if len(prql)*3 > cStringBufferLength {
+        cStringBufferLength = len(prql) * 10
+    }
+
+    // preallocate the buffer
+    cstr := C.CString(strings.Repeat(" ", cStringBufferLength))
+    defer C.free(unsafe.Pointer(cstr))
+
+    // convert the PRQL query to SQL
+    res := C.to_json(C.CString(prql), cstr)
+    if res == 0 {
+        return C.GoString(cstr), nil
+    }
+
+    return "", errors.New(C.GoString(cstr))
+}
+```
+
+## Development
+
+### Headers
+
+The C & C++ header files `prqlc.h` & `prqlc.hpp` were generated using
+[cbindgen](https://github.com/eqrion/cbindgen). To generate a new one run:
+
+```sh
+task build-prqlc-c-header
+```
+
+...or copy & paste the commands from the Taskfile.