| // Copyright 2020 The Wuffs Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| //go:build ignore |
| // +build ignore |
| |
| package main |
| |
| // print-hpd-left-shift.go prints the |
| // wuffs_base__private_implementation__high_prec_dec__lshift_num_new_digits |
| // tables. |
| // |
| // Usage: go run print-hpd-left-shift.go -comments |
| |
| import ( |
| "flag" |
| "fmt" |
| "math" |
| "math/big" |
| "os" |
| ) |
| |
| var ( |
| comments = flag.Bool("comments", false, "whether to print comments") |
| ) |
| |
| // powerOf5 return "5 ** n" as a string. |
| func powerOf5(n int64) string { |
| x := big.NewInt(5) |
| x.Exp(x, big.NewInt(n), nil) |
| return x.String() |
| } |
| |
| func ellipsize(s string) string { |
| if len(s) <= 16 { |
| return s |
| } |
| return s[:8] + "..." + s[len(s)-5:] |
| } |
| |
| func main() { |
| if err := main1(); err != nil { |
| os.Stderr.WriteString(err.Error() + "\n") |
| os.Exit(1) |
| } |
| } |
| |
| func main1() error { |
| flag.Parse() |
| |
| const WUFFS_BASE__PRIVATE_IMPLEMENTATION__HPD__SHIFT__MAX_INCL = 60 |
| const log2log10 = math.Ln2 / math.Ln10 |
| data := []byte(nil) |
| |
| fmt.Printf("static const uint16_t " + |
| "wuffs_base__private_implementation__hpd_left_shift[65] = {\n") |
| fmt.Printf(" 0x0000,") |
| if *comments { |
| fmt.Printf("// i= 0\n") |
| } |
| for i := int64(1); i <= WUFFS_BASE__PRIVATE_IMPLEMENTATION__HPD__SHIFT__MAX_INCL; i++ { |
| offset := int64(len(data)) |
| if offset > 0x07FF { |
| panic("offset requires more than 11 bits") |
| } |
| numNewDigits := int64(log2log10*float64(i)) + 1 |
| if numNewDigits > 31 { |
| panic("numNewDigits requires more than 5 bits") |
| } |
| code := (numNewDigits << 11) | offset |
| |
| p := powerOf5(i) |
| data = append(data, p...) |
| fmt.Printf(" 0x%04X,", code) |
| if *comments { |
| fmt.Printf(" // i=%2d, num_new_digits=%2d, offset=0x%04X, 5**i=%s\n", |
| i, numNewDigits, offset, ellipsize(p)) |
| } else if i&3 == 3 { |
| fmt.Println() |
| } |
| } |
| for i := 1 + WUFFS_BASE__PRIVATE_IMPLEMENTATION__HPD__SHIFT__MAX_INCL; i < 65; i++ { |
| fmt.Printf(" 0x%04X,", len(data)) |
| if *comments { |
| fmt.Printf(" // i=%2d\n", i) |
| } |
| } |
| fmt.Printf("};\n\n") |
| if len(data) > 0x07FF { |
| panic("offset requires more than 11 bits") |
| } |
| |
| fmt.Printf("static const uint8_t "+ |
| "wuffs_base__private_implementation__powers_of_5[0x%04X] = {\n", len(data)) |
| for i, x := range data { |
| if (i & 15) == 0 { |
| fmt.Printf(" ") |
| } |
| fmt.Printf("%d, ", x&0x0F) |
| if (i & 15) == 15 { |
| if *comments { |
| fmt.Printf(" // offset=0x%04X\n", i&^15) |
| } else { |
| fmt.Println() |
| } |
| } |
| } |
| if *comments { |
| fmt.Printf(" // offset=0x%04X\n", len(data)&^15) |
| } |
| fmt.Printf("};\n") |
| return nil |
| } |