git ssb

1
const leb128 = require('leb128').unsigned
2
const Pipe = require('buffer-pipe')
3
const {Iterator, json2wasm} = require('wasm-json-toolkit')
4
5
const EXTERNAL_KIND = json2wasm.EXTERNAL_KIND
6
7
module.exports = function prepare (wasm, include, symbol) {
8
  let globalI64SetterIndex, globalI32SetterIndex, globalGetterIndex, funcSection
9
  let numOfFuncs = 0
10
  let numOfImports = 0
11
  const addedCodeEntries = []
12
  const globalsGetterSetters = []
13
14
  const needExporting = {
15
    'function': [],
16
    'global': []
17
  }
18
19
  const it = new Iterator(wasm)
20
21
  for (const section of it) {
22
    if (section.type === 'type') {
23
      const numOfTypes = section.count
24
      // form: func, 1 param, i32, no return
25
      const globalI32SetterType = Buffer.from([0x60, 0x01, 0x7f, 0x0])
26
      // form: func, 2 param, i32, i32, no return
27
      const globalI64SetterType = Buffer.from([0x60, 0x02, 0x7f, 0x7f, 0x0])
28
      // form: func, 0 param, i32, 1 return
29
      const globalGetterType = Buffer.from([0x60, 0x00, 0x1, 0x7f])
30
      section.appendEntries([globalI32SetterType, globalI64SetterType, globalGetterType])
31
32
      globalI32SetterIndex = leb128.encode(numOfTypes)
33
      globalI64SetterIndex = leb128.encode(numOfTypes + 1)
34
      globalGetterIndex = leb128.encode(numOfTypes + 2)
35
    } else if (section.type === 'import') {
36
      // parse the import section to build the function indexes
37
      const json = section.toJSON()
38
      numOfImports = json.entries.filter(entry => entry.kind === 'function').length
39
    } else if (section.type === 'function') {
40
      // mark functions to be exported
41
      numOfFuncs = section.count
42
      funcSection = section
43
      needExporting['function'] = Array(section.count).fill(true)
44
    } else if (section.type === 'table') {
45
      needExporting['table'] = true && include.table
46
    } else if (section.type === 'memory') {
47
      needExporting['memory'] = true && include.memory
48
    } else if (section.type === 'global') {
49
      const json = section.toJSON()
50
      const addedFuncs = []
51
      if (!include.globals) {
52
        include.globals = new Array(json.entries.length).fill(true)
53
      }
54
      for (const i in json.entries) {
55
        const type = json.entries[i].type
56
        const lebIndex = leb128.encode(i)
57
        if (type.mutability && include.globals[i]) {
58
          if (type.contentType === 'i32') {
59
            globalsGetterSetters.push(type.contentType)
60
            addedFuncs.push(globalGetterIndex)
61
            addedFuncs.push(globalI32SetterIndex)
62
            // getter
63
            // size, local count, get_global, index, end
64
            addedCodeEntries.push(Buffer.concat([
65
              Buffer.from([0x03 + lebIndex.length, 0x00, 0x23]),
66
              lebIndex,
67
              Buffer.from([0x0b])
68
            ]))
69
            // setter
70
            // size, local count, get_local, index , set_global, index, end
71
            addedCodeEntries.push(Buffer.concat([
72
              Buffer.from([0x05 + lebIndex.length, 0x00, 0x20, 0x0, 0x24]),
73
              lebIndex,
74
              Buffer.from([0x0b])
75
            ]))
76
          } else {
77
            globalsGetterSetters.push(type.contentType)
78
            addedFuncs.push(globalGetterIndex)
79
            addedFuncs.push(globalGetterIndex)
80
            addedFuncs.push(globalI64SetterIndex)
81
            // 64 bit
82
            // getter high
83
            addedCodeEntries.push(Buffer.concat([
84
              Buffer.from([0x07 + lebIndex.length, 0x00, 0x23]),
85
              lebIndex,
86
              Buffer.from([0x42, 0x20, 0x88, 0xa7, 0x0b])
87
            ]))
88
89
            // get low
90
            addedCodeEntries.push(Buffer.concat([
91
              Buffer.from([0x04 + lebIndex.length, 0x00, 0x23]),
92
              lebIndex,
93
              Buffer.from([0xa7, 0x0b])
94
            ]))
95
            // (set_global $b
96
            //      (i64.add
97
            //        (i64.shl (i64.extend_u/i32 (get_local 0)) (i64.const 32))
98
            //        (i64.extend_u/i32 (get_local 1))))
99
            // setter
100
            addedCodeEntries.push(Buffer.concat([
101
              Buffer.from([0x0d + lebIndex.length, 0x00, 0x20, 0x01, 0xad, 0x42, 0x20, 0x86, 0x20, 0x00, 0xad, 0x7c, 0x24]),
102
              lebIndex,
103
              Buffer.from([0x0b])
104
            ]))
105
          }
106
        }
107
      }
108
      funcSection.appendEntries(addedFuncs)
109
    } else if (section.type === 'export') {
110
      // export the memory
111
      const addedExports = []
112
      if (needExporting['memory']) {
113
        const funcExp = generateFuncExport(`${symbol}memory`, 0, 'memory')
114
        addedExports.push(funcExp)
115
      }
116
117
      // export the table
118
      if (needExporting['table']) {
119
        const funcExp = generateFuncExport(`${symbol}table`, 0, 'table')
120
        addedExports.push(funcExp)
121
      }
122
123
      // export functions
124
      const funcs = needExporting['function']
125
      for (let index in funcs) {
126
        index = Number(index)
127
        const funcExp = generateFuncExport(`${symbol}func_${index + numOfImports}`, numOfImports + index, 'function')
128
        addedExports.push(funcExp)
129
      }
130
131
      // export globals
132
      let globalFuncIndex = 0
133
      for (let index in globalsGetterSetters) {
134
        const type = globalsGetterSetters[index]
135
        const funcIndex = numOfImports + numOfFuncs + globalFuncIndex
136
        if (type === 'i32') {
137
          // getter
138
          const getter = generateFuncExport(`${symbol}global_getter_${type}_${index}`, funcIndex, 'function')
139
          addedExports.push(getter)
140
141
          // setter
142
          const setter = generateFuncExport(`${symbol}global_setter_${type}_${index}`, funcIndex + 1, 'function')
143
          addedExports.push(setter)
144
          globalFuncIndex += 2
145
        } else {
146
          // i64s
147
          // setter high
148
          const setterHigh = generateFuncExport(`${symbol}global_getter_${type}_${index}_high`, funcIndex, 'function')
149
          addedExports.push(setterHigh)
150
          // setter Low
151
          const setterLow = generateFuncExport(`${symbol}global_getter_${type}_${index}_low`, funcIndex + 1, 'function')
152
          addedExports.push(setterLow)
153
          // getter
154
          const getter = generateFuncExport(`${symbol}global_setter_${type}_${index}`, funcIndex + 2, 'function')
155
          addedExports.push(getter)
156
          globalFuncIndex += 3
157
        }
158
      }
159
      section.appendEntries(addedExports)
160
    } else if (section.type === 'code') {
161
      section.appendEntries(addedCodeEntries)
162
    }
163
  }
164
  return it.wasm
165
}
166
167
function generateFuncExport (name, index, type) {
168
  const setterHigh = new Pipe()
169
  const fieldString = Buffer.from(name)
170
  leb128.write(fieldString.length, setterHigh)
171
  setterHigh.write(fieldString)
172
  setterHigh.write(Buffer.from([EXTERNAL_KIND[type]]))
173
  leb128.write(index, setterHigh)
174
  return setterHigh.buffer
175
}
176