1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162636465666768697071
import Stream from 'https://deno.land/std@0.132.0/node/stream.ts'
export default function largeObject(sql, oid, mode = 0x00020000 | 0x00040000) {  return new Promise(async(resolve, reject) => {    await sql.begin(async sql => {      let finish      !oid && ([{ oid }] = await sql`select lo_creat(-1) as oid`)      const [{ fd }] = await sql`select lo_open(${ oid }, ${ mode }) as fd`
      const lo = {        writable,        readable,        close     : () => sql`select lo_close(${ fd })`.then(finish),        tell      : () => sql`select lo_tell64(${ fd })`,        read      : (x) => sql`select loread(${ fd }, ${ x }) as data`,        write     : (x) => sql`select lowrite(${ fd }, ${ x })`,        truncate  : (x) => sql`select lo_truncate64(${ fd }, ${ x })`,        seek      : (x, whence = 0) => sql`select lo_lseek64(${ fd }, ${ x }, ${ whence })`,        size      : () => sql`          select            lo_lseek64(${ fd }, location, 0) as position,            seek.size          from (            select              lo_lseek64($1, 0, 2) as size,              tell.location            from (select lo_tell64($1) as location) tell          ) seek        `      }
      resolve(lo)
      return new Promise(async r => finish = r)
      async function readable({        highWaterMark = 2048 * 8,        start = 0,        end = Infinity      } = {}) {        let max = end - start        start && await lo.seek(start)        return new Stream.Readable({          highWaterMark,          async read(size) {            const l = size > max ? size - max : size            max -= size            const [{ data }] = await lo.read(l)            this.push(data)            if (data.length < size)              this.push(null)          }        })      }
      async function writable({        highWaterMark = 2048 * 8,        start = 0      } = {}) {        start && await lo.seek(start)        return new Stream.Writable({          highWaterMark,          write(chunk, encoding, callback) {            lo.write(chunk).then(() => callback(), callback)          }        })      }    }).catch(reject)  })}