[vtable] Add pure Go example of GitHub repo vtable.

_example/vtable/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"github.com/mattn/go-sqlite3"
+	"log"
+)
+
+func main() {
+	sql.Register("sqlite3_with_extensions", &sqlite3.SQLiteDriver{
+		ConnectHook: func(conn *sqlite3.SQLiteConn) error {
+			return conn.CreateModule("github", githubModule{})
+		},
+	})
+	db, err := sql.Open("sqlite3_with_extensions", ":memory:")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("create virtual table repo using github(id, full_name, description, html_url)")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	rows, err := db.Query("select id, full_name, description, html_url from repo")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var id, full_name, description, html_url string
+		rows.Scan(&id, &full_name, &description, &html_url)
+		fmt.Printf("%s: %s\n\t%s\n\t%s\n\n", id, full_name, description, html_url)
+	}
+}

_example/vtable/vtable.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/mattn/go-sqlite3"
+	"io/ioutil"
+	"net/http"
+)
+
+type GithubRepo struct {
+	ID          int    `json:"id"`
+	FullName    string `json:"full_name"`
+	Description string `json:"description"`
+	HtmlURL     string `json:"html_url"`
+}
+
+type githubModule struct {
+}
+
+func (m githubModule) Create(c *sqlite3.SQLiteConn, args []string) (sqlite3.VTab, error) {
+	err := c.DeclareVTab(fmt.Sprintf(`
+		CREATE TABLE %s (
+			id INT,
+			full_name TEXT,
+			description TEXT,
+			html_url TEXT
+		)`, args[0]))
+	if err != nil {
+		return nil, err
+	}
+	return &ghRepoTable{}, nil
+}
+
+func (m githubModule) Connect(c *sqlite3.SQLiteConn, args []string) (sqlite3.VTab, error) {
+	return m.Create(c, args)
+}
+
+func (m githubModule) DestroyModule() {}
+
+type ghRepoTable struct {
+	repos []GithubRepo
+}
+
+func (v *ghRepoTable) Open() (sqlite3.VTabCursor, error) {
+	resp, err := http.Get("https://api.github.com/repositories")
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	repos := make([]GithubRepo, 0)
+	if err := json.Unmarshal(body, &repos); err != nil {
+		return nil, err
+	}
+	return &ghRepoCursor{0, repos}, nil
+}
+
+func (v *ghRepoTable) BestIndex(cst []sqlite3.InfoConstraint, ob []sqlite3.InfoOrderBy) (*sqlite3.IndexResult, error) {
+	return &sqlite3.IndexResult{}, nil
+}
+
+func (v *ghRepoTable) Disconnect() error { return nil }
+func (v *ghRepoTable) Destroy() error    { return nil }
+
+type ghRepoCursor struct {
+	index int
+	repos []GithubRepo
+}
+
+func (vc *ghRepoCursor) Column(c *sqlite3.Context, col int) error {
+	switch col {
+	case 0:
+		c.ResultInt(vc.repos[vc.index].ID)
+	case 1:
+		c.ResultText(vc.repos[vc.index].FullName)
+	case 2:
+		c.ResultText(vc.repos[vc.index].Description)
+	case 3:
+		c.ResultText(vc.repos[vc.index].HtmlURL)
+	}
+	return nil
+}
+
+func (vc *ghRepoCursor) Filter(idxNum int, idxStr string, vals []interface{}) error {
+	vc.index = 0
+	return nil
+}
+
+func (vc *ghRepoCursor) Next() error {
+	vc.index++
+	return nil
+}
+
+func (vc *ghRepoCursor) EOF() bool {
+	return vc.index >= len(vc.repos)
+}
+
+func (vc *ghRepoCursor) Rowid() (int64, error) {
+	return int64(vc.index), nil
+}
+
+func (vc *ghRepoCursor) Close() error {
+	return nil
+}