|
| 1 | +import sys |
| 2 | +import numpy as np |
| 3 | +import segyio |
| 4 | + |
| 5 | +# Purpose is to check that all fields behave correctly if set to values from the |
| 6 | +# range of largest, positive values (sign bit is 0) or of smallest, negative for |
| 7 | +# signed types values (sign bit is 1). |
| 8 | +# |
| 9 | +# Values in all integer fields are set using increasing or decreasing numbers |
| 10 | +# respecting the bounds of the field type (32-bit signed integer, 64-bit |
| 11 | +# unsigned integer, etc.). The first field is using the smallest allowed value |
| 12 | +# of its type, if numbers are increased, or the largest allowed value, if |
| 13 | +# numbers are decreased. See actual code for the details. |
| 14 | + |
| 15 | + |
| 16 | +def main(): |
| 17 | + if len(sys.argv) < 3: |
| 18 | + sys.exit("Usage: {} [file] [type]".format(sys.argv[0])) |
| 19 | + |
| 20 | + filename = sys.argv[1] |
| 21 | + type = sys.argv[2] |
| 22 | + |
| 23 | + if type == 'inc': |
| 24 | + # negative values are increasing |
| 25 | + value_sign = -1 |
| 26 | + diff_sign = 1 |
| 27 | + elif type == 'dec': |
| 28 | + # positive values are decreasing |
| 29 | + value_sign = 1 |
| 30 | + diff_sign = -1 |
| 31 | + else: |
| 32 | + sys.exit("Type must be 'inc' for increase, 'dec' for decrease") |
| 33 | + |
| 34 | + spec = segyio.spec() |
| 35 | + samples = 4 |
| 36 | + spec.sorting = 2 |
| 37 | + spec.format = segyio.SegySampleFormat.IBM_FLOAT_4_BYTE |
| 38 | + spec.samples = range(samples) |
| 39 | + spec.ilines = range(1) |
| 40 | + spec.xlines = range(5) |
| 41 | + |
| 42 | + def calculate_value(field, field_size, diff): |
| 43 | + defaulted = [ |
| 44 | + segyio.BinField.Unassigned1, |
| 45 | + segyio.BinField.Unassigned2, |
| 46 | + segyio.BinField.Format, |
| 47 | + ] |
| 48 | + if field in defaulted: |
| 49 | + return None |
| 50 | + if field == segyio.BinField.ExtEnsembleTraces: |
| 51 | + return 5 |
| 52 | + if field == segyio.BinField.ExtSamples: |
| 53 | + return samples |
| 54 | + if field == segyio.BinField.ExtendedHeaders: |
| 55 | + return 0 |
| 56 | + |
| 57 | + if field == segyio.BinField.ExtInterval: |
| 58 | + return 1125899906842594.0 * value_sign |
| 59 | + if field == segyio.BinField.ExtIntervalOriginal: |
| 60 | + return 1125899906842593.0 * value_sign |
| 61 | + |
| 62 | + sizes = [1, 2, 4, 8] |
| 63 | + if field_size not in sizes: |
| 64 | + raise ValueError( |
| 65 | + "Unsupported field {} / field size {}".format(field, field_size)) |
| 66 | + |
| 67 | + unsigned = [ |
| 68 | + segyio.BinField.Samples, |
| 69 | + segyio.BinField.SamplesOriginal, |
| 70 | + segyio.BinField.SEGYRevision, |
| 71 | + segyio.BinField.SEGYRevisionMinor, |
| 72 | + segyio.BinField.FirstTraceOffset, |
| 73 | + segyio.BinField.NrTracesInStream, |
| 74 | + segyio.TraceField.TRACE_SAMPLE_COUNT |
| 75 | + ] |
| 76 | + if value_sign < 0: |
| 77 | + if field in unsigned: |
| 78 | + # negative values can't happen, calculations go from 0 and up |
| 79 | + base = 0 |
| 80 | + else: |
| 81 | + # in 2-complements notation lowest value is binary 1000...0000 = 0x8000...0000 |
| 82 | + base = 2 ** (field_size * 8 - 1) |
| 83 | + else: |
| 84 | + if field in unsigned: |
| 85 | + # all bits can be used to represent number |
| 86 | + base = 2 ** (field_size * 8) - 1 |
| 87 | + |
| 88 | + # note: logic slip in the current implementation |
| 89 | + inconsistent = [ |
| 90 | + segyio.BinField.Samples, |
| 91 | + segyio.BinField.SamplesOriginal, |
| 92 | + segyio.BinField.SEGYRevision, |
| 93 | + segyio.BinField.SEGYRevisionMinor, |
| 94 | + segyio.TraceField.TRACE_SAMPLE_COUNT, |
| 95 | + ] |
| 96 | + if field in inconsistent: |
| 97 | + base = base - 1 |
| 98 | + else: |
| 99 | + # highest bit is reserved for sign |
| 100 | + base = 2 ** (field_size * 8 - 1) - 1 |
| 101 | + |
| 102 | + return base * value_sign + diff * diff_sign |
| 103 | + |
| 104 | + def calculate_header(header_dict, header_field_offsets, value_diff_step): |
| 105 | + prev_field = None |
| 106 | + value_diff = 0 |
| 107 | + for field in header_field_offsets: |
| 108 | + if prev_field: |
| 109 | + field_size = field - prev_field |
| 110 | + value = calculate_value(prev_field, field_size, value_diff) |
| 111 | + if value is not None: |
| 112 | + header_dict.update({prev_field: value}) |
| 113 | + value_diff += value_diff_step |
| 114 | + prev_field = field |
| 115 | + |
| 116 | + binheader = {} |
| 117 | + binvalues = [int(field) for field in segyio.BinField.enums()] |
| 118 | + binvalues.append(3601) |
| 119 | + calculate_header(binheader, binvalues, 1) |
| 120 | + |
| 121 | + with segyio.create(filename, spec) as f: |
| 122 | + tracevalues = [int(field) for field in segyio.TraceField.enums()] |
| 123 | + tracevalues.append(241) |
| 124 | + tr = 0 |
| 125 | + for _ in spec.ilines: |
| 126 | + for _ in spec.xlines: |
| 127 | + traceheader = {} |
| 128 | + calculate_header(traceheader, tracevalues, tr + 1) |
| 129 | + |
| 130 | + f.header[tr] = traceheader |
| 131 | + f.trace[tr] = np.zeros(samples, dtype=np.single) |
| 132 | + tr += 1 |
| 133 | + |
| 134 | + f.bin = binheader |
| 135 | + f.text[0] = "" |
| 136 | + |
| 137 | + |
| 138 | +if __name__ == '__main__': |
| 139 | + main() |
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