Search device, search method, program, and information recording medium

A method for searching a recorder recording a text file that includes an array of a plurality of lines sorted in an order of keys, each of the keys being included in each of the plurality of lines, each of the lines including a newline placed at an end of the line, the method comprising:

• receiving a pattern for performing a search, the reception being performed by a search device;
• setting a head position and an end position of the text file to a lower limit and an upper limit of a search range, the initialization being performed by the search device;
• making calculation of a middle position between the lower limit and the upper limit, the calculation being performed by the search device;
• making acquisition of, from the text file recorded in the recorder, a middle line that:
• (x) starts at or before the calculated middle position;
• and
• (y) ends after the calculated middle position,
• the acquisition being performed by the search device;
• outputting, when a key included in the acquired middle line matches the received pattern, the acquired middle line as a result of the search, the output being performed by the search device;
• and
• controlling by:
• (p) re-setting the head position of the middle line to the lower limit when the key included in the acquired middle line is greater than the received pattern, the re-setting being performed by the search device;
• (q) re-setting the end position of the middle line to the upper limit when the key included in the acquired middle line is less than the received pattern, the re-setting being performed by the search device;
• and
• repeating the calculation and the acquisition when the position shifted backward from the upper limit by a length of one newline comes before the lower limit, the repeating being performed by the search device,
• wherein the search device outputs, if the position shifted backward from the upper limit by the length of one newline does not come before the lower limit, a result of the search to an effect that a line matching the received pattern is not found.

A non-transitory computer-readable information recording medium recording a program for causing a computer that comprises:

• a recorder recording a text file that includes an array of a plurality of lines sorted in an order of keys, each of the keys being included in each of the plurality of lines, each of the lines including a newline placed at an end of the line
• to:
• receive a pattern for performing a search;
• set a head position and an end position of the text file to a lower limit and an upper limit of a search range;
• make calculation of a middle position between the lower limit and the upper limit;
• make acquisition of, from the text file recorded in the recorder, a middle line that:
• (x) starts at or before the calculated middle position;
• and
• (y) ends after the calculated middle position;
• output, when a key included in the acquired middle line matches the received pattern, the acquired middle line as a result of the search;
• and
• control by:
• (p) re-setting the head position of the middle line to the lower limit when the key included in the acquired middle line is greater than the received pattern;
• (q) re-setting the end position of the middle line to the upper limit when the key included in the acquired middle line is less than the received pattern;
• and
• repeating the calculation and the acquisition when the position shifted backward from the upper limit by a length of one newline comes before the lower limit, and
• output, if the position shifted backward from the upper limit by the length of one newline does not come before the lower limit, a result of the search to an effect that a line matching the received pattern is not found.