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However, in accepting such obligations, You may act only 171 | on Your own behalf and on Your sole responsibility, not on behalf 172 | of any other Contributor, and only if You agree to indemnify, 173 | defend, and hold each Contributor harmless for any liability 174 | incurred by, or claims asserted against, such Contributor by reason 175 | of your accepting any such warranty or additional liability. 176 | -------------------------------------------------------------------------------- /pycgen.py: -------------------------------------------------------------------------------- 1 | 2 | # 3 | # Copyright 2014 Celtoys Ltd 4 | # 5 | # Licensed under the Apache License, Version 2.0 (the "License"); 6 | # you may not use this file except in compliance with the License. 7 | # You may obtain a copy of the License at 8 | # 9 | # http://www.apache.org/licenses/LICENSE-2.0 10 | # 11 | # Unless required by applicable law or agreed to in writing, software 12 | # distributed under the License is distributed on an "AS IS" BASIS, 13 | # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 | # See the License for the specific language governing permissions and 15 | # limitations under the License. 16 | # 17 | 18 | 19 | import os 20 | import sys 21 | 22 | 23 | # 24 | # Compiles and executes the Python code that the generator code has access to. 25 | # Returns the global python environment that must be used between all code runs in a file. 26 | # 27 | def CreatePythonExecEnvironment(): 28 | 29 | prologue = """ 30 | import os 31 | import inspect 32 | 33 | # Empty string for output 34 | g_EmitOutput = "" 35 | 36 | 37 | def EmitStr(string): 38 | 39 | globals()["g_EmitOutput"] += string 40 | 41 | 42 | def EmitLn(line): 43 | 44 | globals()["g_EmitOutput"] += line 45 | globals()["g_EmitOutput"] += os.linesep 46 | 47 | 48 | def EmitRepl(generic, repl): 49 | 50 | # Remove leading/trailing newlines 51 | generic = generic.lstrip(os.linesep) 52 | generic = generic.rstrip(os.linesep) 53 | 54 | # Split into old value and replacement values 55 | r = repl.split(":") 56 | old_val = r[0] 57 | new_vals = r[1] 58 | 59 | # Iterate all replacement values and emit them 60 | vals = new_vals.split(",") 61 | for v in vals: 62 | EmitLn(generic.replace(old_val, v)) 63 | 64 | def EmitFmt(line): 65 | 66 | # Get local variables from calling frame 67 | # This is available in CPython but not guaranteed to be available in other Python implementations 68 | calling_frame = inspect.currentframe().f_back 69 | locals = calling_frame.f_locals 70 | 71 | # Remove leading/trailing newlines 72 | line = line.lstrip(os.linesep) 73 | line = line.rstrip(os.linesep) 74 | 75 | # Format with the unpacked calling frame local variables 76 | EmitStr(line.format(**locals)) 77 | """ 78 | 79 | # Compile the prologue and return the environment it creates 80 | exec_globals = { } 81 | prologue_compiled = compile(prologue, "", "exec") 82 | exec(prologue_compiled, exec_globals) 83 | 84 | return exec_globals 85 | 86 | 87 | # 88 | # Opens a file and returns it as an array of lines 89 | # 90 | def OpenFile(filename): 91 | 92 | try: 93 | f = open(filename, "rb") 94 | lines = f.readlines() 95 | return lines 96 | except: 97 | return None 98 | 99 | 100 | # 101 | # Strips all leading whitespace on a line and treats it as the indent 102 | # 103 | def GetIndent(line): 104 | 105 | lstrip = line.lstrip() 106 | indent_size = len(line) - len(lstrip) 107 | return line[0:indent_size] 108 | 109 | 110 | # 111 | # Executes python code at runtime within the given environment. 112 | # Assumes that the code will be doing nothing but code emits so returns the 113 | # emit output from the python environment passed in. 114 | # 115 | def ExecPythonLines(lines, filename, start_line, python_env): 116 | 117 | if len(lines) == 0: 118 | return None 119 | 120 | # Use the indent from the starting line to prepare all the other lines 121 | start_indent = GetIndent(lines[0]) 122 | indent_size = len(start_indent) 123 | 124 | # Strip leading indentation from all lines 125 | for i in range(0, len(lines)): 126 | line = lines[i] 127 | 128 | # Lines that don't share the same indent could be an error... 129 | if not line.startswith(start_indent): 130 | 131 | # ...unless they're empty lines 132 | line = line.lstrip() 133 | if len(line) == 0: 134 | lines[i] = "" 135 | continue 136 | 137 | print(filename + "(" + str(start_line + i) + "): Bad leading whitespace indent") 138 | return None 139 | 140 | lines[i] = line[indent_size:] 141 | 142 | # Run python code with shared global state for entire file 143 | python_env["g_EmitOutput"] = "" 144 | code = "".join(lines) 145 | exec(code, python_env) 146 | 147 | output = python_env["g_EmitOutput"].splitlines() 148 | if len(output) == 0: 149 | return None 150 | # Prefix the output with indentation inferred from the generator 151 | output = [ start_indent + line for line in output ] 152 | output = os.linesep.join(output) + os.linesep 153 | 154 | return output 155 | 156 | 157 | # 158 | # Quick and dirty, line-by-line parsing of an input file looking for Python generator code-blocks 159 | # to execute. Returns the modified file as a set of lines. 160 | # 161 | def ParseInputFile(python_env, filename): 162 | 163 | lines = OpenFile(filename) 164 | if lines == None: 165 | return None 166 | 167 | new_lines = [ ] 168 | 169 | in_emit_output = False 170 | in_python_code = False 171 | python_lines = [ ] 172 | python_start_line = 0 173 | python_indent = 0 174 | 175 | for i in range(0, len(lines)): 176 | 177 | line = lines[i] 178 | line_lstrip = line.lstrip() 179 | 180 | # Detect and skip start and end of emit output from previous runs 181 | if line_lstrip.startswith("//$pycgen-begin"): 182 | in_emit_output = True 183 | continue 184 | if in_emit_output and line_lstrip.startswith("//$pycgen-end"): 185 | in_emit_output = False 186 | continue 187 | 188 | # Copy lines from old to new, ignoring emit output from previous runs 189 | if not in_emit_output: 190 | new_lines.append(line) 191 | 192 | # Detect start of new python code block 193 | if line_lstrip.startswith("/*$pycgen"): 194 | in_python_code = True 195 | python_lines = [ ] 196 | python_start_line = i + 2 # +1 for skip over "pycgen", +1 for 1-based indexing 197 | python_indent = GetIndent(line) 198 | continue 199 | 200 | # Detect end of python code block 201 | if in_python_code and line_lstrip.startswith("*/"): 202 | in_python_code = False 203 | 204 | output = ExecPythonLines(python_lines, filename, python_start_line, python_env) 205 | if output != None: 206 | new_lines.append(python_indent + "//$pycgen-begin" + os.linesep) 207 | new_lines += output 208 | new_lines.append(python_indent + "//$pycgen-end" + os.linesep) 209 | 210 | # Copy lines in python code blocks 211 | if in_python_code: 212 | python_lines.append(line) 213 | 214 | return new_lines 215 | 216 | 217 | # Parse command-line arguments 218 | if len(sys.argv) != 3: 219 | print("Use: pycgen.py ") 220 | sys.exit(1) 221 | input_filename = os.path.abspath(sys.argv[1]) 222 | output_filename = sys.argv[2] 223 | 224 | # Parse the input file and generate any required code 225 | python_env = CreatePythonExecEnvironment() 226 | output_lines = ParseInputFile(python_env, input_filename) 227 | if output_lines == None: 228 | print("ERROR: Couldn't open file " + input_filename) 229 | sys.exit(1) 230 | 231 | # Write the result 232 | try: 233 | output_file = open(output_filename, "wb") 234 | output_file.writelines(output_lines) 235 | except: 236 | print("ERROR: Couldn't write to file " + output_filename) 237 | sys.exit(1) 238 | -------------------------------------------------------------------------------- /readme.md: -------------------------------------------------------------------------------- 1 | 2 | pycgen 3 | ------ 4 | 5 | This script allows you to embed Python in your C-style comments that generates code right after the comment. You can add comments to your file: 6 | 7 | /*$pycgen 8 | dot = """ 9 | inline cmp_math_fn T dot(T2 a, T2 b) 10 | { 11 | return a.x * b.x + a.y * b.y; 12 | } 13 | """ 14 | 15 | EmitRepl(dot2, "T:float,double,short,int") 16 | */ 17 | 18 | Run the script with: 19 | 20 | pycgen.py 21 | 22 | The input file is copied verbatim to the output file with the following generated code next to it: 23 | 24 | /*$pycgen 25 | dot = """ 26 | inline cmp_math_fn T dot(T2 a, T2 b) 27 | { 28 | return a.x * b.x + a.y * b.y; 29 | } 30 | """ 31 | 32 | EmitRepl(dot2, "T:float,double,int,short") 33 | */ 34 | //$pycgen-begin 35 | inline cmp_math_fn float dot(float2 a, float2 b) 36 | { 37 | return a.x * b.x + a.y * b.y; 38 | } 39 | inline cmp_math_fn double dot(double2 a, double2 b) 40 | { 41 | return a.x * b.x + a.y * b.y; 42 | } 43 | inline cmp_math_fn short dot(short2 a, short2 b) 44 | { 45 | return a.x * b.x + a.y * b.y; 46 | } 47 | inline cmp_math_fn int dot(int2 a, int2 b) 48 | { 49 | return a.x * b.x + a.y * b.y; 50 | } 51 | //$pycgen-end 52 | 53 | You can see an example of its use at-large in ComputeBridge, here: https://github.com/Celtoys/ComputeBridge/blob/master/cbpp/inc/cbpp/Math.h 54 | 55 | This is great for simulating generics in situations when you can't use a language with them. The benefits are: 56 | 57 | * Much friendlier and far more powerful than the embedded C pre-processor. 58 | * Allows 3rd parties to use your code without requiring this script. 59 | * Visible code foot-print for all explicitly generated instantiations (unlike C++ templates). 60 | * Each implementation can be stepped-through in a debugger. 61 | 62 | Some drawbacks: 63 | 64 | * Requires the pre-process on your code. Should be fast enough though, given the script exempts large swathes of code looking for the gen signature. 65 | * Obviously not as good as a decent generics implementation for your language. 66 | --------------------------------------------------------------------------------